97 Buick Lesabre Code P0300 and P0171

[bomber19]

I have 2 codes, P0300 and P0171, The car runs good until you go a long distance, then when you shut it off and start it back up again it will start to stumble and finally quit, If you leave it cool for about 1/2 hour it will finally start and run....but not real well...enough to get home with. I've checked the fuel pressure and that's OK..but the MAS sensor has a crack at the top...could that be my problem??
Thanks :?

[Fritz]

MAF sould be the problem, but would usually do it most of the time, not just after shutting it off and letting it heat soak.
If both codes are current, then the P0171 is most likely causing the po300 misfire code. I would clear the codes and see if only one comes back. If only the misfire comes back, then the lean may have been in there for a while and is not really related to your problem.
If you are SURE fuel presure is good while it is acting up, you may have bad oxygen sensor, crank position sensor, ignition module or computer (PCM).
Also take a fuel sample and look for contamination.

[bomber19]

Thanks Friz for the response!!! The car does stumble a lot even when it's cold but once you get going it straightens out..I'll try the MAF 1st!! Thanks again

[Fritz]

Let us know what happens with your Buick.

[KaylaAnneKay]

I have a 94 buick park avenue that has an idle problem. I recently had the harmonic balancer replaced and ever since it likes to idle high and hold high rpms during driving or sometimes when it gets down to normal rpms either by itself while idling or when i come to a stop it starts to struggle and a couple times it has died. I have looked at all the vaccum lines and they are all attached so i checked the accelerator arm and that seems fine. Looked at the intake manifold and everything seems fine there. I do know i have an exhaust leak from where the donut gasket goes but that was like that before the balancer replacement and it didnt have this problem. Any ideas, maybe harmonic balancer on too far or not enough? Also it doesnt want to communicate with a scanner. Also i dont have a service engine soon light on anymore.

[carriedi]

just because you said you have this problem after replacing your harmonic balancer I would take a good look at your crank sensor. (and the connector) Make sure it's still lined up good and tight. That being said, it is very common for this computer to go out. I would use a scanner and look at your TPS, fuel trims, O2 sensor...

A vacuum leak is a common cause for high idle. The unmetered air will cause the O2 sensor to read lean so the PCM will add fuel to fix the exhaust from running lean. More air and more fuel at idle means more rpm's.

You could try a hard reset on the pcm and see if the idle returns to normal after driving it and relearning the idle

Why did you have the balancer replaced if it didn't have this problem before?

[KaylaAnneKay]

The rubber that connected the balancer to the pulley part had finally broken apart so i was getting a loud scrapping sound from it, because the pulley part was pretty much free spinning.