As I said in the video, there are variables. The best thing to do is to make a vacuum leak on an engine with a MAF and a MAP and see what happens. In fact I guess I need to do that :)
So what does it mean if the IAC% stays in the 40-60% range regardless of engine speed? Is it stuck? How is the percentage calculated? Is it the amount of control being sent by the PCM or is it monitoring a position sensor similar to TPS? Thanks all
Most likely not, as the IAT sensor has little effect on the af ratio(maybe 5% correction). Most IAT sensor codes are accompanied with NO driveability problems.
Seriously, thanks again. It's hard to get so much information compiled so thoroughly in one place and you have immensely contributed to my knowledge over the course of your book and each one of your videos. It's taken a lot of my concern away about working with some of the more sophisticated vehicles being produced today. I really appreciate it.
Hey, I want to thank you very much without seeing this video. I’ve been chasing a vacuum leak for almost a year and a half and it was weird because it go away and then sometimes it comes back. I couldn’t find the vacuum leaks and it was saying I had a pretty good size vacuum leak then I seen this video about the I a C and I check that and sure enough mines was staying stacked open at times, basically it wasn’t working properly. Thank you very much. Keep educating people. Because when I would stop at a stop sign or a light, it would start shake shaking rough Eileen. When I turned on the heater or the lights, it would do the same thing just don’t know how happy I am. Thank you again.🎉
Hi Paul I love your approach to every diagnostic explanation,like I mentioned before ,you explain a simple vacuum leak on MAP and MAF system like reading Cinderella story to a six year old.No stone unturned.I know that you are a hockey fan...your team Penguin and my team Canucks were the Stanley hopeful :( what happened?Philadelphia or LA?They suck. Waiting for your vacuum case study
Single cylinder miss also happens due to EGR lines clogging, what happens is there will be high egr flow to one cylinder only which would also lead to misterious miss.I have seen this in honda's.
A MAP,,, might it also think like, 3.0L at 0PSI and X RPM... So then the computer knows it might be 2.8L at -2PSI at the same RPM. Figures are totally out of the blue.
Hi i got my answer after thinking a while, more air and Gas will increase the idle,(in MAP), more air and less fuel(on MAF will be lean condition ) that is why idle is low. If i am wrong pls advise.
Great video! That vacuum leak on cold starts are also real common on toyota corollas 03-08 on the 1zz-fe engines, where the intake gasket leaks only when its below certain temperature.
Yet again coming to find scannerdanner saving my ass, I'm chasing my tail on coil packs because I solved one issue relating to arcing coilpacks so I'm stuck on ignition wasting time and money, turns out my stupid catch can ate an o-ring and was causing a vacuum leak. I love that SD doesn't spoon feed you answers but rather teaches you how to think.
Great comment, thank you so much. Not everyone sees it this way my friend. Most want to be spoon fed the answer only without caring about thr process. Appreciate you
Glad, I am the first who watched this video. In Map engine, when there is a leak, ECM compenstates that air by adding more fuel, (i got that point) but dont know why it will ideal high. can u pls advise.
It will idle higher because there is more air and fuel going into the engine. The air is from the vacuum leak and the fuel is from the MAP sensor voltage change causing the ECU to increase injector pulse. Depends on the size of the leak because the computer is going to close the idle air control valve to bring the idle back down.
Mr Danner, Will you hear an rpm change with a speed density engine that utilizes an afr sensor doing a propane enrichment test for vacuum leak since it is able to react so quickly?
Thanks so much, on other note, I have quesiton, it would be helpful if you can answer me. when u do smoke test, I assume some of the cylinder will be in intake or exhaust stroke even if we had first cylinder in TDC, this means i will always find smoke coming out in exhaust or in throttelbody , is my understanding correct.
I think your hypothesis about low idle vacuum leak with MAF would only apply if you unplugged the O2 sensor. Otherwise the fuel trims will shoot up in response to the unmetered air, resulting in a high idle. Do you unplug the O2 sensor when diagnosing vacuum leaks?
Actually there is vacuum in the crankcase of my 95 mustang 5.0. now I'm trying to isolate the issues: a blown manifold gasket? or are there other possibilities like a blown head gasket? symptoms are: weak engine, shaking idle, about 17 in Hg at idle, the reading floats slowly between 16,5 and 17.5 in Hg. no external leaks detected (with smoke, water or carb cleaner).
variable intakes can also cause lean issues paul, check my video out for this 6 cylinder BMW x5 E53 ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-OxpDLwu4T3s.html&feature=plcp
WE NEED YOUR HELP I HAVE A 2003 MODEL GOLF THAT HAS A POOR MIXTURE AND WHEN I SPRAY THE BRAKE CLEANER INTO THE INLET MANIFOLD IT GOES TO NORMAL.THE ISSUE IS I CHANGED THE GASKET AND IT DOES THE SAME. I SPRAY ON THE PLASTIC INLET MANIFOLD IN THE SOLID PLASTIC AND IT DOESN'T SEEM TO HAVE A CRACK!!!!!!!!!!!!HOW CAN THE SPRAY PASS THROUGH THE SOLID PLASTIC AND BE SEEN BY THE O2 SENSOR?
Hey scanner fanned I got a 6.0 ls truck motor and the codes I have are a knock sensor, and a random misfire I checked fuel trims when cold and hot the short terms are good but the long term are around 5% at cold and 9-10 when warmed up. I can’t figure it out does the knock sensor have something to do with it? I changed plugs and wires and fuel pump because it went out.
Do you have any videos on YT or on your premium that deal with very slight shaky idle problems? I'm really struggling with diagnosing those, both my family cars have the type of slightly uneven idle that won't throw codes, fuel trim look ok, no obvious vacuum leaks when using propane/smoke machine. Car runs perfect whenever, it's just that very slight idle problem. I'm really struggling because they arent dead misses. It's the sort of feeling that you sit in a car and just feel the idle isn't right, you know? Maybe every once in a while you feel a dlight shake. Its not a choppy MAF related idle caused by vacuum. I'm having trouble pulling any useful data from my scan tool. It feels like there must be some sort of an imbalance in the air fuel mixture so if you havr any case studies on very slight shaky idle that would be great. Thank you for your help.
Let's move this to my forum www.scannerdanner.com It is free to join and we can definitely help you. I have 28k global members and hand picked moderators who've been with me for years and know my material inside and out and are there to help me help you guys. It is just too difficult to offer back and forth messages here on RU-vid with stuff like this and we also can't share pictures and images here like we can on the website. Hope to see you there!
@@ScannerDanner thanks so much for the reply. I've posted it there! Hopefully it'll get some attention as I'm really curious to learn. All the best, Paul!
The crankcase vaccum leak on a truck that u were referring to did it happen to be a dodge magnum series engine like the 3.9, or 5.2, 5.9 engie cause they have a plenum pan gasket that used to blow out all the time and would suck the oil right out of the crankcase leading to all kinds or misfire codes and spark knock! Saw alot that customers were using premium fuel to stop the pinging! Great vids man!
Wow that’s a tremendously helpful classroom session ! An internal vacuum leak on a V-type engine is tough ! Thanks for sharing this Premium training with us !!
I'm trying so hard to retain this. I have a 171 and 131 code. Only thing it could be is Intake leak. I can watch this 100 times but when I goto the truck and scan tool I can't remember any of this. It's me I ha e a hard time retaining Info. My truck falls on its face shifts bad. I've changed the 02s entirely new exhaust system new Maf no visible leaks. 09 3500 6.0 vortec. Common for intake leaks. I've checked feel pressure. It's either injectors or intake leak. But idk how to eliminate one or the other once I get out there. This is my 10th time watching.
Falling on its face and shifting bad is not a symptom of a vacuum leak. What does fuel pressure do during a wide open throttle snap to redline? Does it drop?
@@ScannerDanner no it stays right at 50psi. And I guess falling on its face is not the right term mybe. It has no power. Struggles under load and hills. In park or neutral snap throttle high rpms feels fine but idles rough. I thought at first mybe fuel pump but my data points to vac leak. My trims improve when I raise the rpm. I have 2 codes. Po171 and 131. All new 02s and exhast system and have traced 02 circuit all the way back to computer and no bad wires. Reason for all this i bought truck cheap. Needed manifolds back cats were melted out. I fixed my misfires fixed exhaust and know this 171 131 codes and driveability issues. I can't look at my tcm and hope my Trans is fine I think it is and engine issue causing Trans issue not Trans issue and engine issue. Only has 120k if I dident have these codes I would look at Trans but with these codes and my research, my driveability issue and it running rough is related to codes. I hope lol. So falling on its face is not what's its doing. Just low power struggles driveability issues. Starts fine idles rough and low which is another sign I think. Flat rds with little load Trans shifts fine. But my fuel gauge with koeo goes up to like 58 ans sits at 50. At idle it sits around 50 bounces around a little which is weird but could be gauge. At snap throttle amd wot it dosent drop below 50. Idk if haveing duel tanks and 1 not hooked up would be a cause to anything? The auxiliary tank on almost all dump truck this age are rotted out and un hooked. I have good fuel pressure so I don't think so but have to atleast through it in there. And thank you for your reply. You have taught me so much ty
@jesserousseau2481 struggles under load and no power is NEVER from a vacuum leak. Do the O2 at wide open throttle test for me. Should be 800mv + the entire time you are at wide open throttle. This will be our guide on where to go next
@@ScannerDanner I think my scanner only reads volts. I'm waiting on. New good scanner in the mail. But at wot my 02s will go up to .800 .900 then drops down to .100 in an out. At idle b1 has a decent wave pattern from . 800 to .100. B2 wave pattern is not the same and has a horrible wave pattern goes from .800 to .400 never going down to .100. My trims Yesterday were ltft was .17 stft -3 0 +.3. Both banks Today ltft is .8 stft same -3 0 +3 both banks. I have a hard time explaining im sorry.
@@ScannerDanner hear a better description. Ltft b1 -16 at idle. Drops to -21 with rpm Stft b1 -3 to 0. With rpm pretty much stays at 0. Ltft b2 -16 at idle drops to -21 with rpm. Stftb2 -3. To .0 at idle with rpm stays about .0. Both banks are affected. 02sb1s1 .900 to .001at idle stays around .900 with rpm. beautiful wave pattern. 02sb2s1 is .900 to .006. Horrible wave pattern and can definitely see something not right. With rpm it will still bounce not go to .900 like b1. But my code points to b1? I'm pretty sure it's injectors. I have a good 50psi reading with fuel gauge and snap throttle. Been told I could need my fuel alcohol % reset. Never herd of it. Also I just replaced the entire exhaust. Manifolds and gaskets back new cats muffler everything. It was doing it before so I doubt it. But manafold was leaking really bad before. I've also thought of bad pcm. When I got truck I found the starter power wire pretty much welded to the manafold shorted bad. Starter was bad had to replace starter and wire. I did that right when I got the truck so idk of that caused it or if it was had before. Of pcm was bad wouldn't I get other codes? Also I can't clear the codes. I wanted to clear them and tey and get a freeze Fram or something but won't clear. I've spnt the past week watching probly 30 40 hrs of your content. I've got it down pretty good but my scanner is limited. I can't check misfires or injectors. Sorry for last response it dident make much sence. I've had this at all the shops in town and all say idk. I also get alot of smoke out tail pipe. Told that's a sign of Injectors and no my head gasket is fine.
No sir. There are not enough blowby gases to create a rich condition. You will have lean conditions, positive fuel trim numbers and potentially a single cylinder misfire (which was most common)
oh wow. thanks. ok. i have a 4.3 vortec and cant fix my rich condition. i will still check if i get vacuum on my oil stick tube because its easy and im out of ideas. only other possible issue i have is injectors flow but i dont have a machine to do that. i could only do a balance test and it was ok. checked everything else and didnt find anything wrong @@ScannerDanner
@@ScannerDanner 1997. No leaks on the regulator. Despite pressure dropping quite fast like from 4.2 bar to 3 in 10 minutes or so. If i stare at the gauge i cant see it dropping. If i leave and come back it already dropped. But no fuel dripping out on intake. So i assume it loses pressure inside the tank. On one of the spider legs it had a leak that only happened when the injector was activated so it was hard to figure out. It was a bad conection from the injetor to the plastic line. Fuel trims got a lot better after fixing that and cleaning injectors. Went from -30 ST constantly and -18 LT to -8 And -18. When engine is full hot it gets a little better. Around 0 ST and - 15 LT. MAF reading also gets lower and closer to expected at idle
@@brunopecego5297 okay cool. Two things. 1. Did you change the oil after you fixed the rich condition from the leaking injector poppet? 2. What are your fuel trim readings with the MAF sensor unplugged?
I have some comments and I hope you will accept you with open arms 1. Please speak slowly. So we can understand what you say. It is not all your channel subscribers and your followers who are fluent in English. 2. Please activate the captions for all your videos. To show what you say on the screen. And lay your idea to all subscribers of your channel and your followers on best
The captions have been activated for all videos and you can even add captions in your native language if you like. Thanks for the constructive criticism! I've done better over the years (I think)
