Haven't had the car running for about a month getting the front bumper repaired. "But" before that the car would not stay running. It would start and stumble after a few seconds and then cut off. Now, a month later air cleaner off, it starts up just fine but after a little warm up time it stumbles, or dies, until given it a little gas and get a "little" more rpm's on the engine and runs fine above idle. Symptom has changed from a month ago. Fuel delivery seems fine. I'm figuring the MAF needs cleaning as a place to start. I tried to remove the whole assembly but can't get the dad blamed thing off. The stainless steel clip at the back is cleared but seems the rubber grommets don't want to let go. I guess I'll just unscrew the MAF sensor by itself. If not the MAF sensor, and checking voltage to it, does anyone have any suggestions. Has recent cam, crankshaft sensors as well as the RCM.

UPDATE @5:15PM........Sorry I did forget to mention that I had pulled a code P0101. Mass Air Flow A circuit range/ performance.

 

Watched a YouBoob video on removing and cleaning the MAF assembly. Didn't realize there is a securing bracket that has to be released in order to remove the MAF. Life just got a little easier. ( Dumber than dirt! )

 

Removed the MAF and cleaned everything with MAF Cleaner. Reassembled everything and ran great for a a few minutes including idle until it warmed up. The it started hesitation after warming up unless I gave it some gas to keep it running. No problems above idle. Erased code and still get P0101. Tomorrow I'll use some carb spray and see if there are any vacuum leaks. There is a hose previous owner had replaced coming from the top valve cover down to the rear of the engine block that is suspect cause it is low quality zip tied at top and mushy.

 

Sounds like a symptom of a bad EGR valve might do when the engine warms up. I'll check that also tomorrow but it does not show up as an EGR code.

 

Or a failing CPS, since heat seems to be a trigger ?

 

EGR system might be fine, how about a vac leak ?


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Still have to check later today. No time right now.

 

You are not looking closely. The symptom-function troubleshooting technique demands you look at the bold text and ask yourself, "What is the ECU getting from the MAF/IAT that is thinks is wrong/out of range"?

Go look at the six codes in the list that the ECU can generate having to do with the MAF/IAT. This is the most vague one of all. But we KNOW that the data the MAF/IAT is giving the ECU is NOT being trusted by the ECU. This is a case where I might clean the MAF (I have little confidence in doing so) but I'd more likely replace it. (And if it was the IAT half, you'd have a P01xx code.)

I know I lecture people like this: "A code from a sensor means the sensor might be bad, OR the sensor might be telling the truth and something else is actually bad causing the code, so do not change a sensor just cause the code mentions that sensor". But in this case, given your symptoms and the code, I would lean towards the MAF being bad. Unfortunately, we don't know what exactly the ECU does not like in the data coming back, but you could hook up a live data code reader and SEE what you see.

I also know that MAF codes can be a result of a Throttle body that is lying to the ECU about what position it is in, the ECU accepts the TB data and then sees too much or too little air flow and blames the MAF, based on the lies of the TB. This should NOT happen, as the TB has two data outputs, so the ECU knows if they are different, the TB is lying. But if the 5 volt feed to the TB is bad, both outputs would be off equally, fooling the ECU.

Based on the fact it smooths out at certain throttle positions, I don't think it's the crank sensor, I think it's fuel-air mix related and the ECU uses the MAF and TB, working together, to manage that ratio, but the ECU can't do that effectively if EITHER device provides bad data.

If it were MY car, unless I am missing something or ignorant about the history of the car (both possibly true), I'd order a new MAF. I mean, I'd try to clean it but if that did not work, I'd still assume the MAF is at fault. I could be wrong, but again, the clues so far imply a bad fuel/air ratio. Could the Crank sensor be a flake such that, at low speeds, the ECU can't run the engine right but can at high speeds? I do not know the answer to that question, so put in your spare BOSCH sensor and find out, since it takes ten minutes. But I bet $20 it it not the CPS.

 

With the engine cover off (everything else buttoned up, don't let the spray go into intake), lightly spray some 'carb' cleaner around the rubber air lines (vac lines). IF the throttle jumps or makes it stall, you may have found the culprit. I did not forget the seems fine during (before) warmup.

I am guessing you DID a throttle body 'reset'?


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Hmmmmmm! Throttle body reset???? Uhhhh well maybe if I ever heard of something like that! Guess I'll have to look that up!

Update 18 Aug @ 3:50pm EST.......Doing it now and letting it sit for 30 min before attaching the battery cables.

 

As always very good information and advice! Thankks Pizzaguy!
What ever happened to all the cars where you just have someone crank the handle on the crankshaft and it starts with a little spark advance? LoL Maybe life wasn't so easy back then after all. Wifey kept breaking her arm! (Another LoL)

 

Everytime I hop on "Animal" and tap the starter, and it's fuel-injected, electronically controlled engine rumbles to life in less than 3 seconds, my desire to return to 1969 fades a little more.

 

Well that didn't work out so good! Hooked battery up, turned ignition on for about 3 or 4 minutes, turned key off and then started and it started right up. Let it idle for about 4 minutes and then gave it some gas. Smooth acceleration and everything was working beautiful. When temp got about 1/4 way up it started same ole hesitation and could not make it run at all. Tried several times and it just died. Last try it just cranked and cranked and then popped back thru the MAF! Closed hood and tomorrow I'll change the CPS with a new Bosch.

 

Let us know the solution, please.

 

Yes I will. I just ordered a new MAF and will be here Sunday! Can't believe how cheap they are! Amazoo $23 delivered!

 

BINGO!

Look at what you typed, you said the car runs fine to a certain temperature, then goes to hell. I do know that there is a temperature where the ECU changes from "open" to "closed" mode. It will take a lot of reading, but I know there is a transition that happens. It sounds to me that once the ECU goes to "closed mode" and the O2 sensors' input is important, the ECU has a hard time running the engine. This would imply that the readings from the O2 sensors are causing trouble. SO the question is, are the O2 sensors lying or are they seeing something about the O2 level (too high or too low) and is the ECU going too far trying to compensate for this?

I think you just posted the clue of all clues - too bad none of us have the expertise to explain what is going on.