2002 GP running bad

[JWJR]

I'm trying to help a buddy get his 2002 Grand Prix with the 3.8 non SC running right. A few days ago he was out driving and the car stalled and took him a while to get it to start up. when it started he drove it to his grandpas house he took it and had the codes read at auto zone. and he only remembered that it had to do with the MAF and that the auto zone guy didn't think that the MAF would make it stall out. so he changed the fuel filter and drove it around town for a bit and it did alright. so my buddy picked it up and drove it to his house, which which is about 10 mile out of town, when he pulled into his drive way it did again. he got it to start but it wouldn't idle with out giving it gas. so he pulled it into the garage.

Then he called me. it went out today with a code reader and a fuel pressure gauge i rented from auto zone. i pulled the codes and it had P0102(MAF code) and P0108(BARO/MAP code). i cleaned the MAF sensor and put it back in and cleared the codes and told him to call me if the CEL comes back on. i also checked fuel pressure just to rule that out and it had 48 psi with KOEO and KOER. so i dont think it has a fuel pump going out.

So what would cause these two codes to come on together or are they two different problems that just happened to come up a the same time? What are some things i can look at I'm a Ford guy not GM?

Thanks
JW

[SilvaMan61]

he got it to start but it wouldn't idle with out giving it gas.

idk if this will solve it all but ^^ that sounds like a vaccum leak. check out the lines

[JWJR]

Oh year forgot to put in that when i was there checking the fuel pressure the car started up and idled it did have a slight misfire.

[ZR1Vette09]

On a side note, it should be "running badly"

[SDGTP99]

So, check all your vacuum lines. regap or replace the spark plugs, and get the car scanned again, somewhere else. Im betting u need a new MAF sensor.

[JWJR]

ZR1 english was never my best subject. if the codes come back i will get him to replace the plugs and wires...the wires looked orginal. i will check the vac lines and i told him when i cleaned the MAF that some time it fixes them but not always.

[RyanL]

had the exact same problem with same code, had to replace maf sensor. when it first started up idle speed was bouncing around like a bad idle air conrol.

[pur3vil]

some of these cars used both MAP and MAF to monitor air,
MAP - measures barometric pressure in the intake
Master Pro Ignition 2MS15 - MAP Sensor | O'Reilly Auto Parts
MAF - measures relatively how much air is entering the system
Cardone 74-50008 - Mass Air Flow Sensor | O'Reilly Auto Parts

If youv'e cleaned the MAF, check the vacuum line to, and / or, replace the MAP sensor too.

[matt5112]

the car uses the MAF until the MAF is unplugged or deemed unusable by the PCM.

Only then does it use the MAP.

MAF > speed density in the eyes of the PCM and ease of tuning.

[pur3vil]

the car uses the MAF until the MAF is unplugged or deemed unusable by the PCM.

Only then does it use the MAP.

MAF > speed density in the eyes of the PCM and ease of tuning.

Ohkay, so both are possibly bad? if the MAF is intermittant and it's falling back to a bad MAP the car has nothing to judge from and will die which could be why it's throwing both codes.

speeeeeed denssity... sounds better in my opinion

[matt5112]

If GM made quality electronics then MAF wouldnt be a problem.

Easiest test for the MAF is to unplug.

If it runs better, the MAF is bad.

[RyanL]

^^not exactly true. with mine unplugging it didnt change a thing. but replacing it was the solution.

[jaredbos 1]

i just did the exact same thing on my car.. the maf was good.. but the map was blown in half... detach the map and check if it looks good. or take it somewhere to get tested.. this took care of the idle problem.. but not the misfire.. still looking for the solution on that one