2000 Pontiac Grand Prix Runs Rough

MMC2011LM

MEMBER
2000 PONTIAC GRAND PRIX
256,000 MILES

I have a 2000 Pontiac Grand Prix SE with a 3.1L V-6. The car has 256,000 miles on it, but the motor only has 84,000 on it. I replaced it awhile back. The car was running fine & then started running rough so I put my scan tool on it & got several codes. The codes was a P0135 so I went ahead & replaced the downstream & upstream oxygen sensors, the second code was a P0420 so I replaced the converter, the third code was a P0102 so I replaced the mass air flow sensor, & the last code was a P0443 & I replaced the canister evaporative purge valve. I cleared all the codes & then disconnected the battery & the P0102 & P0443 code still comes up & the car still runs rough. This is the third (MAF) sensor within the last 2 years I put on it & the wires & connectors are good. The motor surges ( rpm goes up & down & lights dime when it does) & when I drive it, it runs fine until I have to stop then the car shuts off, but will crank back up have a few times. Why is the motor surging & why is the 2 codes (P0102 & P0443) keep coming up? I know the motor is surging cause of the codes, but how do I fix this problem? Could the ECM ( computer) be bad?

3 Replies

HMAC300

MECHANIC
48,601 POSTS

First clean the throttle plate on both sides with choke cleaner and iac hole. Then check duct work from maf to throttle for holes and all hoses and grommets on engine even if they are for something other than water. Any of that can cause a maf sensor code. This also includes oil filler cap and dipstick tube. Also look for blockage at air filter etc. As far as evap test for a poor connection or if it actually is getting power it may not be. Turn ign off, disconnect evap turn ign on then probe wire for power if power it's ok if not you have to search for reason like a poor connection at pcm, broken wire et.