Hi Everyone!

I just purchased a 1999 Pontiac Grand Am (2.4L, 4 cylinder, automatic transmission) with 72000 miles. I drove it from California to New Mexico with no problems and drove it to work for its first week. However, last week, it started acting funny. After being stopped (at a stop sign or stop light), when I would press the gas, the car would hesitate and go. The next day, I notced that it did the same thing on the highway (you would let off the gas, when you would give it gas again - it would kinda hesistate). I took it to Pep Boys on Friday and they couldnt find anything with the car. On my way home, the car started doing the same thing yet this time, it stalled when I gave it gas to go at a stop light; turned on right away. The service enginge soon and trac off light came on as well. I took it back to Pep Boys (this time thinking they could diagnose the problem). They got a "biometric pressure sensor" code which they cleared to see if it would come on again. It didnt - so again they sent me home; claiming they saw no problems with the car; they said they may have tripped something when they checked the car the first time. I turned it on again this morning to go to the grocery store. This time I felt it kinda bumping.....when I pressed the brake pedal, the service engline light and trac off light came on.

Has anyone had this same problem...or something similar??? I am hoping to take it to another car repair shop tomorrow (very disappointed with Pep Boys) to see if they can find the problem. However, if anyone has had the same problem, then maybe I can help the shop find something.

BTW - I like the closeness you all have in this forum. I hope I can be as good a member as all of you all are.

Welcome to AF!!

If they got a MAP code then there may be a problem with the Mean Atmospheric Pressure (MAP) sensor. This can cause a number of issues with the drivability of the car. Just because they are not getting a code you may need to take the car to a dealer to have it checked. PEP boys are OK for some things but drivability issues like you have may require a dealer or at least a better mechanic.

Based on your description this issue could also be due to a throttle position sensor. Finally but doubtful the Engine control module could be going bad. (computer) but I really don't think that is the case.

Thank you so much, GTPDad. I plan on taking it to the dealer to have it checked out. I hope its not a big problem.....or expensive. I will keep you informed.

It could be a bad wheel bearing as well, usually when those lights come on together that is the case.

It turned out to be a bad MAP sensor. :-) The diagnosis (dealer) was $85, the part (original equipment) was 90 and the installation (not at the dealer) was $19. Car is running normally now.

cficare - it was a bad MAP sensore that needed replacement. The dealer told me that they checked everything regarding the trac off light but they could only see that it had been on in the history and nothing was wrong (at the time of service) that would trigger it on. Thanks for your input and your help.