High vacuum reading at idle I have had P0171 and P0174 Stingr69 wrote: ↑ Fri Oct 11, 2024 2:29 pm You want to have a vacuum canister that pulls all the way in at a vacuum level that is 2" less than your intake manifold vacuum at idle or the timing will jump around. 50. Some interpret as a vacuum and some as actual barometric. I readjusted the rockers today and still no better. Start engine allow to idle < 1 minute = 0. Identify Issues: Lower readings, below 17 Can it be that just my idle from the caburetor is causing the variations? The cam has about 6 degrees of overlap and I don't know if this has an affect on vacuum readings or This chart shows vacuum readings you might see and what they mean. you should be able to take your finger and wiggle it up and down a little. I mostly see 18 at idle with I've tuned a couple of cars besides mine, and they all had similar cams, kpa at idle has been between 50-52kpa so far, at around 800rpm, base timing set at 17* on the idle cells. Register. So that's an element already in play. Rings were cast, he mentioned, for a quick break in period. That is what I’m seeing most of the time, 12-13 Kg/h. If anyone has a means, please check your engine vacuum reading at idle and post results on this thread. General engine tech -- Drag Racing to Circle Track. That's quite high, IIRC, and it's also normal for my car at idle and matches exactly what it normally shows, from before this problem developed. My gauge always read -10 . Jump to Latest 64K UMMM, NO! I have been doing some reading on what I'm gonna do to it tho. As for manifold vacuum, absolutely yes, that's something I'll work with. This is a 15 WRX with no mods or tune completely stock. Runs smooth at 2500 rpm. The next question I have is my scanner is an actron and it Idle vacuum reading will drop the higher you go in altitude also. 5 ish. There are several possible causes of a high MAP sensor reading, including a faulty MAP sensor, a vacuum leak in the intake manifold or vacuum lines, a clogged or dirty air filter, or a problem with the wiring or My MAP reading was about 4. rechecked all the other ports again and plugs in place and tight. It is important to address these issues promptly to prevent potential engine performance yes,map sensor is fine,it is a Mapdaddy 4 bar map from diyautotune,map and baro readings around 100-101kpa with engine off,boost numbers are near same as on the gauge. On the other hand, lower readings could mean there is a restriction in the intake, or again, a MAF sensor issue causing underreporting of the air entering the engine. I tried the manifold vacuum, just idled way to high. Don't see any issues revving to redline: car actually just shoots right up there. We’ve said it before, but an engine vacuum gauge is an extremely valuable tool. the car idles at 900rpm at around 51-52kpa pretty good, so i wanted to lower that a tad to get a little bit more In terms of idle quality, this simple move from ported to manifold vacuum increased the idle vacuum in Neutral 2 inches from 13 to 15 inches Hg, and the in-gear idle vacuum is much more stable at nearly 10 inches Hg. The most vacuum I saw was at 1 turn out (started at 1 1/2). May 17, 2010, 09:19:33 AM. If the reading is still A high MAP sensor reading can cause a variety of issues, including reduced engine performance, decreased fuel efficiency, and increased emissions. When at idle, the normal manifold vacuum for any engine in good working condition is about 18 to 22 in. Jumping between 09-19 (min/max values) where it's practically illegible like in the first video. Monitor the MAF reading on the tool. Most mod motors pull 18-20 inches of vacuum at 750-850 rpm. 02:37: The high RPM vacuum area of the map is an area that the engine won’t be driven in under normal circumstances. Jump to Latest 11K views 7 replies 7 participants last post by zax Mar 28, 2016. Well, that's still not badanother cam I had in my 360 intially was a Crane MaxVelocity cam, with the following specs: 216/228, 272/284, . D. Find the reason behind the high idle and you'll find the missing vacuum. James Stratton January 7th, 2023 What Brought me this question is that my cruise control stopped worki thought it was a broken vacuum line I did some repairs to some brittle lines leading to the cruise control actuator but that didn't take care of it I had a code thrown regarding the large leak and canister circuit. I'm sure this code gets set at idle. I could be incorrect as when I datalogged I didn't see anything to raise my eyebrows but will do it again. Resident Adviser @ WTF Tuning, LLC 2002 FORESTER S 1998 FORESTER S . Ensuring that the boost gauge reads zero or at atmospheric pressure during idle can help maintain the engine’s longevity and overall performance. 5 psi at idle . 7 down to ~12 at WOT without jumping around). A high, steady vacuum reading is the sign of a healthy engine. When readings exceed 22 inHg, inspect the exhaust for blockages. My maf reading is in lbs and not grams. Stock heads, intake, exhaust. After doing so, the RPMs at idle are sitting around 1100–1400. Also the MAF shown at idle Intermittent drops in vacuum at idle and under cruise could indicate a sticking valve, and needle drop of vibration under acceleration can indicate a bad valve or valveseat. 3 V8 with a 4l60-E. I just installed a new vanos and did everything the instructions said but it doesnt seems right driving. 4190 posts · Joined 2004 Add to quote; Only show this user Ok after reading that I've come up with two things. I highly recommend the EFI University online courses along with other tuning literature. In most cases, highly efficient, electronically controlled engines produce a slightly higher vacuum reading than do mechanically controlled engines. I was expecting a higher vacuum. And, to a certain point the more initial/idle vacuum, TO A CERTAIN POINT, increases idle and off idle vacuum, TO A POINT. Hook up your hand vacuum pump to the EGR valve and slowly apply a vacuum. Just looking for some input on a slightly high idle between 900-1k rpms on my 06 rev up. On the idle question, since i installed a holley heat shield. Previous topic - Next topic. The car won't idle at less than 1500 rpm. Also, your idle is high at 1k. The first step in fixing a high LTFT is to check for vacuum leaks. The needle goes between 11 and 13 inches and is pretty quick between the readings not really fast but you can follow it easy. 1975 W200 360/np435/203/triple tanks/dual-batts, bought new. Use the vacuum gauge to diagnose engine performance. However, you should check your MAF regularly and keep your car’s MAF sensor reading properly to ensure your safety when driving. It makes me High idle. I checked my vaccum reading yesterday, truck fully warmed, idling at 600 rpm. To high-speed vacuum readingshould at least equal idle vacuum. No. When idling, it should Regarding the drilled idle plates, the Barry Grant I'm using has the Idle-Eaze feature which mimics the effect of drilled primary plates. With ENG at idle, slowly increase engine speed to 3,000 RPM. 1 inch of mercury by the way is a measurement that is roughly equal to 0. 6 and now during winter, I'm idling at -8. so I've been doing ALOT of reading on this problem trying to better understand LTFT. At idle, the needle bounces rapidly (almost violently for lack of a better term) between 2 and 12 hg. . I started it and timed it to about 8 degrees. 75 lbs is correct. Usually, vac-uum at 2500 will be greater than idle vacuum. A vacuum leak Vacuum too high is no issue. Problem is at idle it is very rich and about 15" of vacuum. Engine runs rough too and usually needs some throttle to keep up the rpm. Overheats, even cruising on the highway. If it was a vacuum leak my STFT would be high too and they would drop when I increase load. 20in is pretty normal. I would agree that idle vacuum seems low, I would want to see it up around 15, depending on cam grind. 2 inHg. e. since I put it under load it drops drastically, like 15 is a borderline high (low) reading. I hooked the car up to a scanner for some live data and I am seeing the vanos reading late at idle and the camshaft position at -12 to -13 KW. It levels off around 15 when you kick the rpm's up to an estimated 2000 or so. 0/302, 5. Reading Vacuum Levels: Normal vacuum readings for most gasoline engines range from 15 to 22 inHg at idle, while abnormal readings indicate potential issues such as leaks or exhaust blockages. WyomingWagon Discussion starter. And for the map when they were seeing 30 kpa at idle my 9. readings that change quickly indicate sticky valve guides, burned valve sets, or leak in head gasket. 5 ish, sometimes it will be -10 ish,And sometimes it will be -9. 5 turns ported fitting on carb is pulling 7 in. I had "Booster Steve" at Power Booster Exchange in Portland Oregon rebuild my unit. This a normal reading—between 17 and 22 inches of mercury. Sometimes after being on the throttle for a while and then Does anyone know what the reading for the camshaft position is suppose to be at idle. My next step is to try and reduce idle speed, see if ported vacuum is reduced and idle mixture screws have more effect, and if carb dies when put in gear at lower high kPa map reading at idle. 15" is ok if it's steady, probably around a 270(+/-5*) adv duration cam. Tags icp idle pressure. But need to keep idle around 900 to 1,000 rpm to get into gear without stalling. I had a efi source 3bar map in it. Save Share Reply Quote Like. 2. Vacuum Instrumentation Intake manifold vacuum can be measured with a mechanical gauge, electronic pressure transducer, or through the engine management system via a diagnostic scan tool. Moderator: Team. 6. If we notice our car idling at a higher-than-normal RPM, it often points to a problem within the vehicle’s engine management system. another thing that will screw the idle up is having the linkage that connects the three carbs too tight. A steady, high reading typically indicates proper tuning, while fluctuations or unusually low readings can imply Typical vacuum in a 1. James Stratton January 7th, 2023 What Brought me this question is that my cruise control stopped worki thought it was a broken What is your vacuum reading at idle? Is it about the same as other vehicles in your area (depends on the altitude above sea level where you live). In fact, it wasn't until Colt45ws pointed out that the vacuum readings from my ECU are calculated, rather than measured, that I realized the only way to get an actual vacuum reading from this truck is to hook up a gauge. LTFT +%14 at idle engine warm, this number varies + - %2 or 3. On my scan tool, I could read 37 kpa. Here’s another story that may help out too. Remember that Observe the vacuum reading at idle, as this will serve as a baseline. SJCRoughneck Discussion Start your engine and let it idle. So when somebody told me it should be around 6. I'm leaning toward this possibility more and more as I think about it, because idle doesn't change at all when I disconnect and close off the vac line going to the fuel pressure regulator. 22 at your altitude is pretty good. Air leaks will affect MAF air mass readings in a negative direction (at idle only). UPDATE - Rebuilt the carb because of all the fuel problems. It can also indicate whether the engine’s turbocharger or supercharger is functioning properly. So far I was not Optimal Fuel Injection. Go. If I have vacuum on the ported line I have the idle/throttle opened up too much. 05 mpa at A boost gauge reading at idle can help diagnose issues with the engine, such as vacuum leaks. Have you checked the PCV valve and it's vacuum line? A leaking or disconnected line going to the PCV valve will cause a high idle. 12" manifold vac needs a The instant you let off the gas and the throttle plates close, vacuum will return. A healthy engine usually shows a reading between 17 and 22 inHg at idle. I’m at a i can get the initial idle and timing to around 15 BTDC,1200 RPM, and am pulling somewhere between 25 and 30 vac. The needles would be relaxed and Ford Inline Six, 200, 250, 4. Fluctuations of 3 to 4 inches may be sticking valves. the linkage's function is to open and close the Exactly novadude, i use the ported vacuum for good idle and smoother pulls. i can get the initial idle and timing to around 15 BTDC,1200 RPM, and am pulling somewhere between 25 and 30 vac. If it takes longer for the gauge to return to the same idle reading, your exhaust is Run the engine at idle, low cruise (1000 to 1200 rpm) and high cruise (2500 to 3000 rpm). testing at High Vacuum Readings: May denote a restricted exhaust system. 2014 2. ie numerically higher vacuum readings. They used to With a simple vacuum gauge you'll be able to compare its readings to the map sensor. The needle oscillates RAPIDLY at idle and does this anywhere up the I just installed my vacuum/boost gauge and my car idles at about 15, drops to about 12 when i step on the gas, and then goes to like 22-25 real quickly Log in. The higher the vacuum, the harder the needles are sucked down closed. 91 posts · Joined 2013 Add to quote; Only show this user #5 · Oct 10, 2014. a vacuum) while 60 mph uphill will make for a relatively Also, your idle is high at 1k. This will give you a baseline AFR to build off of. That may or may not be 3000 rpm. If I assume the wrong units and psi values, I'd say a normal idle at normal idle speed would be in the -10 to -12psi range with a small cam I usually find that an idle AFR of between 0. since only at idle I'm experiencing a high LTFT, I believe it has to be a vacuum leak. The idle surges for the moment between when I unplug it and when I cap it off, but then it goes right Sounds like your MAF has a MAP sensor as well and actually measures vacuum; unfortunately, mine does not. Junior Member; Posts: 85; Logged ; vacuum reading at idle. At wide open throttle when there is almost no vacuum in The idle screws were way too rich & the low irregular vacuum was causing the carburetor needle springs to bounce compounding the problem. Engine compression is 160psi across all cylinders. Low readings could also be very late valve Higher-than-normal vacuum at idle is a common clue to overly advanced ignition timing, while low vacuum can indicate retarded timing. Next Last. 1 to -8. the edelbrock carb has two needle valves on springs. This increased the However is it really only 15kpa of vacuum or is it a false reading? This is where I'm stuck. Air mass readings high above 20 Kg/h, which I noticed from time to time, can’t have anything to do with vacuum leaks IMO. When a car experiences high engine load at idle, it’s often a sign of underlying problems like vacuum leaks or faulty components. ClockChoke Discussion starter. 5 power valve might not be right for you anymore Fatten up your idle mixture so it is a bit richer than usual. willy. 9L / 300 - Vacuum at Idle Question - I rebuit my one barrel carter this last weekend and put it on the truck. It’s so valuable, in fact, that OnAllCylinders contributor Lori Sams put together this visual cheat sheet to help you understand common gauge readings. The only reason I'm concerned is because I had to drive a 2018 and its winter idle was sitting at -9. 5hg (which would be about 52 kPa Vacuum gauge should be connected to manifold vacuum at the tap where the transmission modulator goes. I checked the MAF performance on my car. Upon start-up, the idle will be normal (around Finally got a vacuum gauge and plugged it into the vacuum port on my 351W's Performer RPM intake. Adjusted the speed down and had to screw the adjustment screws almost all the way in and idle quality was good and good vacuum. starts up fine when dead coldHolley 4160 with divorced choke. 75 hg is also correct. I guess I can try Finally got a vacuum gauge and plugged it into the vacuum port on my 351W's Performer RPM intake. That reading should be between 17 and 22 inches of Mg (mercury). I'm getting a vacuum reading of 11 at idle in park. hg 3K RPM No load = 17 - 20 in. High Vacuum Indications. Scott . Once I'm on the throttle at speed it's usually quite steady and behaving as expected (14. 8T at idle is approximately -0. 1. When this air is mixed with atomized fuel from the At idle or when decelerating, vacuum is high and the BP/MAP sensor output may drop to 100 Hz (Hertz, or cycles per second) or less. Also my title was a little misleading by high, I meant that -5 psi is higher than -20 psi, whereas negative pressure would be vacuum. For every 1000 ft. Today the gauge started reading at -11 . this is most often caused by a vacuum leak. 5 lower than idle vacuum. Mine runs at 21 with a steady needle. What little I know seems to suggest that the problems are of them not reading high enough. If the oxygen sensor is So if it is affecting your idle quality here's a couple of things you can try to improve it: Try with and without crankase PCV valve Sometimes a 4 hole spacer can help You need a PV 1-1. Again,, assuming its a waddle waddle. Randy- 2002 blaze WRX- sold 2004 Wrx-sold 2011 Wrx limited 99 Fozz- sold Eagle eye crew. Anytime you open up the throttle The vacuum gauge sometimes referred to as an "economy gauge" in the 70's is going to give it's best reading when you find the engine's happy cruise speed. A stock 289-2V should have 19-21"hg at idle in neutral. The key is having a reliable engine vacuum gauge and then knowing how to read it properly. I have it ran directly to the non ported side if my Quick fuel 650. 0 engine running a btr centri cam,v3 ti supercharger, zl1 map sensor. If the EGR valve is If it "runs on" ad 12 BTDC either the idle is too high, there are vacuum leaks or the plugs are too hot. Logging load runs I see the MAF clipping upwards in excess The intake manifold pressure is not speed dependent but rather load dependent. A normal reading at idle usually falls between -15 to -20 inHg, indicating a well-tuned engine A quick snap of the throttle plate should drop the vacuum to around 5 "hg vacuum, and then it should recover to a steady 21 "hg vacuum. I will have to go back and see what happens to the timing when I pinch the pcv hose. vacuum reading at idle? Performance Talk. ) Holley At 2500 rpm in Neutral, the normal high-speed vacuum reading should at least equal idle vacuum. Vacuum readings at idle much lower than normal indicate leakage through intake manifold gaskets, manifold-to-carburetor gaskets, vacuum brakes or the vacuum modulator. SCOTT 1969 CHEVELLE SS396,ORIGINAL #'S With regards to F/I, is there an unsafe range of vacuum you should be reading at idle? I've heard some people say you should be reading 15", or 20", and others say anything In the first pic you can see my MAF reading at idle (600 - 700) it was 3. Jul 25, 2018 #1 I think your timing numbers look about right. My bad I wasn't vacuum at idle. 28Kpa =4 psi. Erratic vac readings at carb Gauge needle bounces violently when trying to get a reading to re-adjust idle circuit. Compared Find the EGR valve and disconnect the vacuum line going to the top of the valve. hg N54 Wastegate What are you guys getting for vacuum readings at idle for your mild 350's. So my reading of . Engine vacuum is normally 'high' around 17-21" during regular driving. Lets start with the high idle. Fo Low engine vacuum can be the result of a lean air/fuel mixture and/or retarded ignition timing. 8. It is If the gauge reads the manifold vacuum behind the carb, the reading will fluctuate a lot, as there it would read mostly the rear cylinders. Quick Tech: How to Read a Vacuum If the vacuum readings are normal at idle, but begin to pulse or flicker as the engine speed is increased, broken or weak valve springs are most likely the problem. In my 13 years as a mechanic, I’ve seen numerous cases where abnormal MAF Stuff like 12/14 initial, with 12/10 vacuum degrees, for 24 degrees IDLE total. Started it and the idle speed was extremely high. no problems driving or idling in neutral. I have an Actron Scanner and have been monitoring the data. I just tried pinching off the PCV hose on 2 other cars with small blocks that are more radical than this one and they both show more vacuum at idle (both read over 15") and pinching the pcv does not cause the engine to want to Proper vacuum specs haven’t changed. Keep in mind, this reading is ideal for stock-cammed engines running at sea level. By increasing rpm, adjusting With vacuum connected to full manifold vacuum your 10 deg of initial timing is ok, but at idle you want 20-22 deg of total advance, i. When using a vacuum gauge to set timing I always leave the vacuum advance connected - you're not setting it to a spec on a balancer. When this air is mixed with atomized fuel from the fuel injectors, engine speed is increased. Sometimes it will be -10. 480, 112 LSA That was a nice torque cam and I was pulling close to what you describe if I recall correctly. I have factory power brakes with a Midland-Ross booster. I swapped the MAF with a friend's known working one - no effect. TBI being a MAP sensor based system will see the leak just like opening the throttle blades and will feed the leak and That would account for high positive fuel trims at idle, as well as loss of vacuum. I have a 1968 Dodge Charger R/T with a 440 hp engine. Repair and continue testing. But as I said earlier, with this cam, don't be alarmed if the vacuum jumps around at low High idle speeds can lead to increased fuel consumption and unnecessary engine wear. Re: high KPa map reading at idle. I have a tuner working with me on this but extra input is always good. Also - the scan tool shows vacuum at 20. Good point on the recomendation of the vacuum being irratic from the manifold area specifically causing the timing to jump around. Resident Adviser @ WTF Tuning, LLC 2002 FORESTER S 1998 7. Hg vac at 850 rpm warm idle speed is 800-850 in park, 650 in drive. At this point I had forgotten to hook up the PVC hose back up. I'm seeing -3. A good place to read vacuum is at the ignition vacuum advance canister or at the carburetor manifold vacuum port. What The cam has about 6 degrees of overlap and I don't know if this has an affect on vacuum readings or not. 9 and 0. Only $100 and very good information. Is it less than other vehicles This whole exchange should go from idle reading to idle reading in 2-3 seconds, tops. C1 & C2 Corvettes - average L-79 vacuum gauge reading and idle questions - what's a good idle vacuum reading at idle for the L-79? Looked everywhere and can't get a good average answer. Barometric conversion is to take reading of atmosphere (key on engine off) and subtract output from that to get vacuum. Edelbrock dual plane manifold (think it's performer 351w. Consequently, that reading should be, between 17 and 22 inches of Mg (mercury). So, I checked and found that my 08 Pilot w/85000 miles had 21 inches of vacuum at idle on a warm motor. Most engines will run 17-21 In/Hg while idling at normal operating temperature. Low Vacuum (below 15 inHg): Indicates potential issues like incorrect jetting I've searched TC and the internet and have found several good websites describing how to interpret various vacuum gauge readings, but none describe what mine is doing. Hg at idle. But, add a long duration non-stock camshaft or other performance related parts, you will soon find out that a stock-rated power valve is not your friend. Vacuum less than -15 inHg at idle would be a cause for investigation. Typically 2 problems. ENG vacuum should be equal to or higher than You have learned about the normal MAF reading at idle g/s – 2 and 7 g/s at idle and 15 to 25 g/s at 2500 rpm. If you're at altitude, these readings may be lower (supposedly by 1 inch of mercury for each 1000ft above sea level, roughly). -20 Hg seems a little low to me for vac reading at idle, as I recall my car pulling almost -30 Hg at idle. off I have the autometer phantom 30 in Hg- 20 psi boost and a stock cam and s-trim. High vacuum may also point to specific issues. hg Idle to 4K RPM (heavy acceleration. -Hg for every 1000 ft. The engine should snap right back to a steady 17- 21 "hg vacuum. So i tired the ported vacuum source, works great. 1 to -9. 29 posts Previous; 1; 2; dieselgeek Guru Posts: 2248 Joined: Tue Sep 09, 2008 8:51 pm Location: Re: high kPa map reading at idle. If you're at altitude, these readings may be lower (supposedly by 1 Okay, I'm going to assume that since no one has responded and I've gotten quite a few looks that there is no one who has checked. I agree anything over 25 inches vacuum seems high at fast idle. 00 at idle they meant grams. I messed with the Idle mixture until it seemed to be running right but I was under the impression that the best way to set the Idle I saw 1. Using a vacuum gauge to tune carbs is becoming a lost art, just like using a dwell meter. Currently it An engine that runs rich at idle can be caused by a bad coolant temperature sensor, a faulty throttle position sensor, a bad mass air flow sensor, a leaking fuel injector, or an engine vacuum leak. Idle vacuum decreases as altitude increases, by a factor of roughly 1 in. In this article, we will take a closer 2015 WRX Vacuum gauge reading -11 at idle. STFT varies up and down a few percent but is usually positive at idle. Adjusted timing and carb and now it idles around 1200 rpm Just installed new 445 stroker and tuning carb idle, specs below. A quick snap of the throttle plate should drop the vacuum to around 5 "hg vacuum, and then it should recover to a steady 21 "hg vacuum. The more efficient the pump, the higher the vacuum reading will be at idle. I can't find any vacuum leaks. The truck is stock. Low engine vacuum can A high, steady vacuum reading, is the sign of a healthy engine. Obviously this isn’t true for huge lopy cams that can barely idle. holding steady at 10-15 “/Hg indicates valve High vacuum readings at idle can indicate several issues within the engine that may signal a potential problem. Working on a 440 that I did not not put together. I ran a 3/4 track grind so low end was a joke. Jump to Latest 15K views 12 replies 4 participants last post by SJCRoughneck Dec 12, 2021. A 4. It has what the previous owner told me is " About the If you were using a mechanics vac gauge,which reads inHg you would see a reading more like 18 inHg . Go Down Pages 1. Once you have the highest vacuum reading, turn both idle mixture Give us a vacuum reading at an idle. Also, when I hooked up my vacuum gauge I couldn't get a reading any higher than around 5-7 inches of vacuum. Hg. The dist. Timing was at fixed angle of 15°. Look forward to your MAP reading or I am having a problem with my 2005 Silverado 5. When your car is running but you are not moving then the engine must continue running at idle speed to keep from cutting out. I have a feeling that you What is the expected vacuum reading at idle? Forced Induction follow ft86club on our blog, twitter or facebook. Idle surge or idle hunting and high idle. With changes in engine A common cause of high vacuum at idle is a tight intake valve clearance, leading to restricted air intake into the engine. The less vacuum,the needles are relaxed and valves opened for more fuel. The idle Kpa was high around 80-85 kpa and wouldn't stay running unless I gave it throttle. Hydraulic lifter bleed-off will manifest as an intermittent vacuum drop at idle, Here are four common techniques to fix a long-term fuel trim high at idle: Check for Vacuum Leaks. Sprayed entire top half with ether and can't find a vacuum leak anywhere. What Are The Vacuum Gauge Readings Telling You Vacuum Gauge Test Readings. My lamco gauge pod shows about -. 75 when the idle is around 850 When the transmission is put in Drive the fluctuations increase upto a 4" sweep. A lean mix at idle can cause surging, and the reading will slowly sweep up and down. G. Other factors such as a clogged air filter, vacuum leaks, or a faulty PCV valve can also contribute to a high vacuum reading at idle. This lead to a high idle. So then I suspected MAF or other input air sensor failure. 0T ( white top pcv) complete engine rebuild 10k miles ago. 1 of 2 Go to page. You can I've tuned a couple of cars besides mine, and they all had similar cams, kpa at idle has been between 50-52kpa so far, at around 800rpm, base timing set at 17* on the idle cells. 3/4 street grind or better. High performance or So now i know i have no vacuum leaks, to double check this i placed my hand over the TB at idle and completely covered it, and the car stalled (as its supposed to) I then A boost gauge reading at idle can help diagnose issues with the engine, such as vacuum leaks. hg Engine at idle > 1 minute = 0. Here are some common vacuum readings and their meanings: High Vacuum (above 20 inHg): Good fuel mixture, but check for air leaks if the engine runs rough. Is this normal for anything other then Identifying Common Idle Issues. That vacuum reading seems low to me, unless my cam is a little more radical than I think. -20 could very well be good Even with those specs the idle vacuum should be better than 65 Kpa. Today i just finished another Goat with dart 225 heads and a 232/236 111lsa cam. With the idle vacuum being so low it has me wondering if perhaps I need to change to a lower power valve, or if maybe the PV is blown. I know the needle should be nice and steady and my idle is around 900 rpm. - Before I put our '68 L71 away for the winter I was somewhat disturbed because I was only pulling about 10-12 Steve, if you have a mighty vac you can connect it to the vacuum can on the dist and see when it starts to advance (vacuum reading) and how much. This I wonder how common it is for MAFs to be failing to plus side of things. If the oxygen sensor is FE & FT Big Block V8 (332, 352, 360, 390, 406, 410, 427, 428) - 15" vacuum reading at idle? - I got my first vacuum gauge yesterday and checked on my 360 vacuum tirwin: if you don't mind my asking, once you pulled & plugged the vacuum retard, what kind of vacuum readings were you getting at idle? dannobee: yup, engines w/higher-overlap cams If all this in an attempt to achieve the same high vacuum reading at cruise as at idle, I seriously doubt that will ever happen as long as your fighting wind Resistance. I marked out my screw driver handle with 1/8 turn dots so I knew how much turn Study with Quizlet and memorize flashcards containing terms like When testing intake manifold vacuum, a low steady reading at idle is likely to be caused by:, Technician A says when if a boost leak causes lower vacuum reading, what causes high vacuum reading? i'm currently reading like 28-29 at idle with an highport sr20de-t basic setup running with s3's. Post by lukep6470 » idle mixture screws don't seem to have much effect on idle after 3. Tags c30 high idle Along with a vacuum pump delete. Here are some common factors associated with high vacuum: Restricted Exhaust: High vacuum readings often indicate that the exhaust system is partially blocked. If you’re at altitude, these readings may be lower (1 inch of mercury for each 1000 ft. Stock engines typically have a high vacuum reading (10-18 inches at idle) and the Holley power valves with higher readings like 6. Please realize that vacuum is dependent on idle High idle vacuum reading. While driving the vacuum will go up and down a lot - mostly according to what the throttle plate is doing. Check the timing belt or chain, depending on the If the idle goes over 800 adjust curb idle screw until back at 800 rpm, recheck idle mixture screws again. The cranking vacuum test also can provide a quick test for PCV restric-tions. Normal Engine: On a good engine, accelerate to around 2000 RPM and then quickly release the throttle. 9 inHG at idle warmed up. Hooked it up and engine died. If there is not vacuum 17-20 in. Vacuum reading vary for lots of reasons, altitude (lower), Evap system purge valve operating (lower), Vacuum readings at idle that are much lower than normal can indicate leaky intake manifold gaskets, manifold-to-carburetor gaskets, vacuum brakes, or the vacuum modulator. When dyno'd all idle circuits were 1 turn out but now 2 Responses to “Engine Vacuum Troubleshooting” . If your MAP sensor malfunctions, the airfuel mixture may constantly alternate between lean (low fuel trim value) and rich (high fuel trim value) — causing a rough idle. Post by dieselgeek » Tue Jun 24, 2014 9:57 pm. Running stock distributor with electronic trigger. With these cars you generally sit between 20-22 at idle out of gear. No It worked fine until recently it's been giving wacky readings, especially at idle/ closed loop. I have been experiencing a shudder at idle, rough shifting, sluggish power, and abnormally low gas mileage. So my upstream o2 sensors are reading rich both banks but my downstream sensors are lean (the lean due to the spacers shown in the picture). ) = 10 - 13 in. This is about 10 inches of vaccum. Your car’s engine may receive insufficient fuel if a bad MAP sensor sends inaccurate manifold vacuum data to the ECM. Low vacuum also can be an immediate clue to a plugged When your engine vacuum gauge fluctuates at idle, you may have a worn valve guide or uneven compression caused by broken rings, leaking valves, or a blown head gasket in one or two cylinders. ( Map sensor provides a vacuum reading via the bluetooth app. The next thing I'd do is hook the vacuum advance back up and adjust the idle mixture screws to achieve the highest vacuum reading at Read the Measurement: Observe the vacuum gauge. , vacuum advance should add 10-12 deg at With my Edelbrock I like to use the ported vacuum port to adjust the idle. when i connect the advance to either upper or lower vacuum ports on the carb the motor revs to full Small Block V8 (221, 260, 289, 5. above sea level ). No codes present. 75 - 4. unmetered air in entering somewhere and making it into the combustion chamber causing the PCM to adjust fuel to equal it. But it doesn't violently GUIDANCE: just 1/16 turn of those throttle screws can make a big difference with IAC readings. b. A steady reading at idle indicates a well-tuned carburetor. 122 posts · Joined 2015 Add to quote; Only show this user #1 · Mar 27, 2016. Currently it Exactly novadude, i use the ported vacuum for good idle and smoother pulls. LTFT at 1500rpm no load, +%9. 95 works best and this often needs to be coupled with a slightly higher idle speed than what you would use in an otherwise stock engine. When in gear, no throttle you'd be 25-30. Save Share Here are four common techniques to fix a long-term fuel trim high at idle: Check for Vacuum Leaks. I think I have the idle mixture set as well as possible and my vacuum reading (at 750 RPM) is just like scenario #3 here: Animated Engine Vacuum Diagnostics Is my cam (specs in Idle Vacuum Question Just curious if this is normal vacuum at idle or not on an all stock 2019, in the summer I usually idle at -10. Thread starter gtiGreateness; Start date Apr 5, 2021; 1; 2; Next. If you find any leaks, you can replace the affected parts. Usually, vacuum at 2500 will be greater than idle vacuum. I have a PCV valve in the driver’s side valve cover going to the rear of the carb base and a vent line on the passenger side valve Also, when I hooked up my vacuum gauge I couldn't get a reading any higher than around 5-7 inches of vacuum. I'm getting 13-14 degrees at an 750-850 idle. 8. The needles would be relaxed and It settled down to around 2400 rpm. I will try and figure Occasional code P0171, lean bank one. -Hg. Hp tuners custom 3bar OS. This is because engine manifold vacuum is usually After IAC steps are in set, focus on idle AFR. This I'm trying to get my idle mixture correct using a vacuum gauge and the vacuum gauge is jumping between 5 - 7 at idle. I tried to block off the IAC port in the throttle body, but it made no difference in the idle speed. I think it may help the community out when troubleshooting pcv or oil leak issues. Idle vacuum can be affected by a number of things, and the first is altitude. If the Map reading was shifted then it would read lower than the real value, given your Uncover the essentials of engine vacuum levels at idle in this comprehensive guide. Then pinch 48 August 2001 A low but steady High MAF readings at idle might suggest a vacuum leak or a faulty MAF sensor reporting more air than is actually present. Glad to see people recommending leaning it out, my only additional advice is to Once you’ve connected the gauge, you should see, a STEADY reading at idle with the throttle closed. Running flawlessly. It shows right on the chart (top part), idle to be to the right side (high vacuum/low MAP voltage) and left to be WOT (low vacuum/high MAP voltage). I set my carb for proper slot transition, i wasnt going to mess with that. the person I bought it from said it had a mild cam installed but everything else At idle the vacuum should read between 18-22. When using a vacuum For example, if you’re seeing vacuums readings at idle of: 15-18 “/Hg and holding steady the timing is retarded too much; advance ignition timing until vacuum returns to normal. I have a high performance 408 SBC stroker with a semi aggressive cam, so I did not expect big vacuum at idle. 491 psi. Just use the vacuum gauge as you dial-in the idle mixture and static timing, and try to tune for the best vacuum you can get at idle in park and in gear, and you'll be fine. We will scrutinize the potential causes, interpret diagnostic signals, and highlight the important roles of specific car parts. The reading should be very steady at idle - no twitches or floating around. There should be no vacuum there at this time. I bought this car "in progress" so here is what I know: 351w circa 1978 rebuilt 1969 heads (PO mentioned he did this to raise compression numbers) Original pistons, new rings and bearings. Idle speed now is 850 rpm in gear and jumps to 975 in Neutral because of the tight torque converter. User Name Mine reads around 20in/hg from my obd2 readout Vacuum readings at idle are crucial for diagnosing the overall health of an engine. Intake System Leakage, Valve Timing, Or Low Compression Vacuum readings at idle much lower than normal can indicate leakage through intake manifold gaskets, manifold-to-carburetor gaskets, vacuum brakes or the vacuum modulator. So the usual 6. Started by willy, May 17, 2010, 09:19:33 AM. Engine Stalling. the car idles at 900rpm at around 51-52kpa pretty good, so i wanted to lower that a tad to get a little bit more Is it fair to say that having a high MAP reading (102 kPa) at idle indicates a vacuum leak? Is it fair to say having a low MAP reading (1 kPa) at idle indicates a fuel pump problem? Main issue with both cars is poor fuel economy and both have had the EGR thermostat changed and next due to have their main thermostat changed. lukep6470 Helpful MS/Extra'er Posts: 129 Joined: Sat Dec 22, 2012 10:13 am. Hey everyone. 5 to 10. (or it's not really at 12*). My STFT C3 Tech/Performance - Engine vacuum and high altitude: Doh. And i also think it's a leak somewhere which would make sense. Note the vacuum readings, and any fluctuations, at each speed. This increased the vacuum but then I had to turn the idle set screw up too much in order for it to easily restart without pumping the throttle. (850 rpm'S) 0 in. psinuse . The vacuum advance was disconnected during testing. 4190 posts · Joined 2004 Add to quote; Only show this user Once you've connected the gauge you should see a STEADY reading at idle with the throttle closed. You’re located at a relatively high Getting ready to see what vacuum reading is at main port on rear of carb. A low vacuum reading means you have poor piston Are you talking about at idle? A fast fluctuation at idle could point to worn valve guides. Any thoughts? since pcvs and crankcase vacuum come up a lot, i thought i would take a snapshot of normal for reference. Issues could range from a vacuum leak, which causes an imbalance in the air-fuel mixture, to a dirty or faulty idle air control valve, which regulates I'm not sure if the reading is barometer or vacuum. Idle rpm's also contribute to vacuum levels, too high, gives a too low Idle. LTFT at 2500rpm no load, +%4. Check the Oxygen Sensor. of elevation above sea level. Vacuum while coasting If your vacuum canister doesn't start adding timing at low enough vacuum, you can have a situation where the amount of advance it does add fluctuates at idle, which in turn I'm trying to understand the fists vacuum reading at idle. Out of all the various cam's I've tried this by far had the best throttle response . Sensor readings at "idle" look normal: TPS - 0 IAC - 0 Vacuum Kpa - 45-55 AFR - 14-16 The car is running slightly lean when I drive around the neighborhood. 2 to -10. has no vacuum to it as is a mechanical advance so thew only port I removed the factory plugs on the Holley was the main in the rear & it's attached to a new hose going to the pcv. The standard range is 16-22in at idle depending partly on altitude. 03 while at idle and as I drove around I saw . The needle oscillates RAPIDLY at idle and does this anywhere up the It is registering vacuum at idle instead of boost. However, my vacuum gauge reads 14. For instance 60 mph going downhill is likely to produce a LOW manifold pressure (i. All of the other readings appear to be in spec; hydrocarbons off idle is somewhere readings that change slowly indicate incorrect setting of idle mixture screw. The vacuum source is via the Progression ignition distributor. Is this indicative of a problem ? Top. What we really need is a different, slightly looser Engine vacuum (hg) = 30 - kPa * 0. Is it less than other vehicles where you live? IF so, you still have a vacuum leak. If anything your high idle will probably result in lower. cranking speed is normal or high but vacuum is low and slightly uneven, the engine probably has low com-pression or retarded valve timing. A Uncover the essentials of engine vacuum levels at idle in this comprehensive guide. The guy had similar vacuum at idle with stock ecu,but car ran better up top,now he feels it a bit slow there,but this cam is designed to give power to 7500. If vacuum at 2500 rpm is less than idle vacuum, disable the EGR system and retest. Types of Vacuum Gauges: Various vacuum gauges, including analog, digital, manifold gauge sets, and handheld devices, cater to different diagnostic needs and preferences. On first startup I noticed a very high kPa reading of in between 80-90 at rpm's from 1100-1700 that were used during the 10 sec run. One common cause is excessively low fuel flow to the engine, A high, steady vacuum reading is the sign of a healthy engine. Understanding MIL and Diagnostic Trouble Codes High MAF readings at idle can be caused by: A dirty or faulty MAF sensor; Vacuum leaks in the intake system ; Leaking or stuck-open fuel injectors; A malfunctioning engine control module (ECM) How does vacuum affect MAF readings at idle? Vacuum affects MAF readings at idle because the sensor measures the mass of air entering the engine. The cam in my car is only about 240@ . He has a trick he does with internal valving. Idle issues has to be one of the most common issues that I get contacted about. That and sorting out a new centrifugal curve to better suit the new engine. The issue is that the Is 1200 rpm to high to get a good vacuum reading ? I thought that stock motors got 21-22 inches at idle and anything with a bigger cam would have less vacuum. High-speed vacuum readings that change may be a result of broken or tired valve springs, while low engine speed vacuum readings tend to be constant. David G Well-known Member. if the linkage is tight it will cause the end carbs to crack open and screw up the idle mix. I believe you are barometric as it would be around 18" of vacuum under normal conditions. Low If you were using a mechanics vac gauge,which reads inHg you would see a reading more like 18 inHg . A low, steady reading indicates a leaking gasket at either the intake or throttle body, leaking vacuum hoses, late ignition timing, or incorrect camshaft timing. Print. Next, hold engine Using the more stable reading I saw a increase in manifold vacuum if I leaned the idle circuit. 8/351W) - Ford 302 strange vacuum reading and idle (Ford E303 cam and Edelbrock carb setup) - Today I try to find out my strange vacuum reading and idle at my 302. Wondering if its a carb issue. Heres whats going on. 454/. Readjusted idle again and back to lousy idle and low vacuum. You can do this by inspecting the vacuum hoses and the intake manifold gasket for cracks or leaks. Does a vacuum reading at idle that fluctuates rapidly between 7 and 10 sound right while in park at 900 RPM He started running it with a carb and had trouble with the idle, then went to a Holley Sniper (which is controlling timing) and is having the same issues. A high, steady vacuum reading, is the sign of a healthy engine. Normal vaccum for a V8 Just installed new 445 stroker and tuning carb idle, specs below. about all you can do is set high idle and run a bit rich. When I put the vehicle under load, the rich condition goes away, so it’s only at Checked the vacuum yesterday and it was around 8in. This and idle adaptations high on the plus side is consistent with air leaks. Inspect the catalytic converter for clogs or damage. 5 will work correctly. 02:44 2 Responses to “Engine Vacuum Troubleshooting” . of increase in altitude, 1 "hg is subtracted from the vacuum reading. You may need to reset your IAC steps after this. when i connect the advance to either upper or lower vacuum ports on the carb the motor revs to full advance timing lights shows 40 degrees with the vac still in the high 20s low 30s. S. It is helpful with cars with lower vacuum signal. Before the valve train adjustment, I had 6 or 7 hg vacuum. Steady low between 5-10 "hg vacuum: This indicates that the engine's intake manifold or the intake gasket is leaking. Drive at the road speed where you got the vacuum gauge to read the best vacuum reading at idle. idle and vacuum are erratic on any long duration cam. I have tuned several Comp 306 cams which is rated at 230/244 on a 112 LSA, that cam has an idle vacuum High ICP Readings at Idle. 3 MAF reading at idle helps the ECU determine the appropriate fuel to inject into the engine. Addressing I think OP knows this, which is why he's stating his apparent issue is that he sees an abnormally high MP reading at idle (20 in-hg) when he is expecting less than 15 in-hg. 97 and . If vacuum at 2500 rpm is less than idle vacuum, disable the EGR For example if the needle vibrates fast enough to be a blur across a range of several inches vacuum that gets better as RPMS increase, the engine MAY have a deadish First off I'd like to say the car seems to be running fine, but I just noticed that my Vacuum readings at idle seem low to me. What is your vacuum reading at idle? Is it about the same as other vehicles in your area (depends on the altitude above sea level where you live). At idle, my MAP sensor reads 40kPa, which mathematically comes to 18hg. Does a vacuum reading at idle that fluctuates rapidly between 7 and 10 sound right while in park at 900 RPM with my combination or should it be higher and/or steadier? I can't get it steadier or higher with idle circuits. Using the more stable reading I saw a increase in manifold vacuum if I leaned the idle circuit. A jumped timing chain or belt is a com-mon cause here. No The idle vacuum reading is a measure of engine health and state of tune. What if my reading is off? If your MAF reading is out of the typical range, here are a few troubleshooting Apparently, the hydrocarbon reading at idle is ~408, with the maximum allowable being 220. That was The idea when these gauges were popular in cars like mid 70's Pontiac Grad Prix. The OP stated the MAP voltage was high at idle and went down as vacuum decreased. 185752 Sent from my SM-G973W using Audizine mobile app vacuum at idle. User actions. I have an idea why it won’t run now with higher vacuum. Perform the test and note the average vacuum reading. 55 bar (-8 psi; -17 inHg). A low You won't get a good vacuum reading with ITB's without a steady idle and it will idle faster than the same cam with a single throttleif a single throttle plate idled at 850, then Steady low between 10-15 "hg vacuum: This reading indicates late valve timing. 3 The issue I'm having is that there's quite a disparity between what the MAP sensor is reading, and what my vacuum gauge is reading (which is on direct manifold vacuum). 8 in the same winter air/temp. 0 in. However my mechanical gauge was reading A quick snap of the throttle plate should drop the vacuum to around 5 "hg vacuum, and then it should recover to a steady 21 "hg vacuum. Driving under load, LTFT is at most + %2-3 O2 sensor voltage appears correct primary ignition circuit, high tension cables, distributor cap or ignition coil. Tune to vacuum, idle quality and plug read, much like you would a carb. Worn piston rings? Adjust the throttle stop screw to achieve optimal idle. The MAF and MAP sensor readings are low for my area sea level. C. The vacuum needle fluctuates right from the start on a cold engine and doesn't improve when hot. 95 on my LTFT and STFTs. I'm wondering what a 'good' vacuum reading should be during acceleration (under load)? While under 'load', say, driving up hill at 55 mph in 4th gear; consistent pressure on the What are cam specs,lrg cam will make for a jumpy idle vacuum reading,i have also seen a bad pcv valve do that. Learn how to diagnose vacuum issues through gauge readings and leak inspections, Normal Boost Gauge Vacuum Reading . Low readings can also be very late valve timing or worn piston rings. Learn how to diagnose vacuum issues through gauge readings and leak inspections, Common reasons for experiencing high vacuum at idle include a vacuum leak in the intake system, a faulty PCV valve or system, or a stuck-open EGR valve. MAP sensor is a very simple device, should be cheap ($10 ish), not worth the effort. gtiGreateness Ready to race! Apr 5, 2021 #1 Hello 2 Responses to “Engine Vacuum Troubleshooting” . Higher elevations may cause slightly lower readings. The figures you saw are set low actually. I believe the cam has been changed but I don't have any specs. For V6, vacuum leaks is included by the MAP sensor already, so that intake vacuum leaks shouldn't have an effect on performance. By accurately measuring the incoming air volume, the MAF sensor enables the ECU to adjust the fuel injection system for optimal combustion, ensuring smooth idling and reducing the chances of stalling. Rough Idle. I've already advanced the timimg. There is a good chance the vehicle has jumped timing. Solutions to Common Issues. proper adjustment is the linkage slightly loose at curb idle. If you have my vacuum advance modifications package, it is all in there. If there is then check for proper EVR (EGR vacuum regulator) operation and vacuum line routing. knpdon asx gqtxyr iqrqji zgcpnt patya nwhy istk kiq olve