98 Pontiac Grand Prix GT Stalls when Hot p0171

[GPDanny]

Here is my situation, when my car heats up around 200F i get this problem where my idle will miss then jump up catching itself(sporadically), also if i rev it to about 3-4k rpms(also at the rpm it has little backfires) when it comes down the car wants to stall. Another thing when i'm driving it after it is hot it will stall while i am stopping( not every stop) it will start back up once it does stall. after this happened it popped up a p0171 code.

so after reading some forums i pulled my MAF and cleaned it, pulled my IAC and cleaned it, replaced my PCV(the mount that holds the MAP in place on top of it had the plastic hold downs for the MAP broken off, still sits in place), took throttle body cleaner and followed all the vacuum lines and didn't hear and rev in the idle. i have a fuel filter to put on but haven't ( check the fuel pressure its at 50 psi with key on engine off and 40 psi with engine on).

none of that fixed the issue, I'm not sure if i should change my o2 sensor next or buy another map sensor mount or pull my fuel pump and check clean the 2 strainers or even another MAF or even an EGR check.. going to the dentist soon and will work on it more when i get home any advice is greatly appreciated.

[danielsatur]

Do a smoke test for unmetered air leaks, and focus on the PCV, EGR, and Air intake systems.

Because of age + mileage, it could be a bad rubber seal, gaskets, or plastic causing the problem.

[olopezm]

WELCOME TO THE FORUM!

Don't do O2 sensors, these are not the cause of the lean bank code. When the problem starts disconnect the MAf sensor (with engine off) from the harness and run the car to see if the problem goes away. If it does then a new sensor is on your near future.

Oscar.