99 Grand Am, too lean, trac off

[jdiem240]

Noob question. My wife's 99 Grand AM SE, auto , 2.4L is running rough. Mechanic found low fuel pressure and replaced the pump ($510.00 installed). Catalytic converter bad replaced for $120.00. Still same problem after warmup...car stumbles while cruising and stalls when stopped. Trac off lights on and code reader indicates fuel too lean, bank 1. I have replaced the fuel filter, front O2 sensor and above mentioned parts. Also have ran a bottle of Seafoam through the fuel system. Checked voltage and resistance on MAP sensor, air temp sensor.
Also replaced the plugs with NGK V Power, new coil packs on Dec 25 04.

I need your collective wisdom...thanks in advance.

[Ridenour]

Could be a bad MAF, or maybe your injectors are partially plugged. If your injectors are really dirty (so dirty seaforam wouldn't be effective to clean it all out), then the pulses will be blocked by the dirt = running lean. I would reccomend an injector flush / clean.

[Forkliftguy]

2.4's don't have MAF sensors. You say you checked the IAT sensor resistance? What value did you get out of it, and second, did you check the resistance through all the temperature ranges? If you take the sensor out of the car and sit the thermistor on an ice cube you shoul get a high resistance setting. Then place the thermistor in a glass of hot water, you should get a very low resistance. Then with IAT unplugged and ignition on you should get 5volts at the plug. Chances are though, like Ridenour said, your injectors (or one at least) could be clogged especially the mileage on the car is particularly high.

Marc

[Werm9]

stalling could be several problems. the main things are: clogged fuel injectors. sticky fuel plate. you can put a bottle of fuel injector cleaning in your tank or spend $60 and get your injectors cleaned. on my old corsica i took it to the shop 3 times cause it was stalling. spend $600 on a recalled computer and the problem was the engine wasnt getting enough air. $600 for nothing