I have a 2000 Pontiac Grand Am with the 2.2L L4 with 140,000 miles on it. After having been driven for awhile and sitting at a traffic light or when making a slow speed turn, the engine will begin to idle rough and die. It doesn't do this all the time, but fairly often. It has never failed to start right back up and idle normally. The fuel filter has been changed and that didn't help. I ran a diagnostic on it and it displayed a P0172 code, System too rich". Could this be from a faulty IAC valve, bad fuel pressure regulator, or maybe the fuel injectors? Thanks in advance.
The idle air control motor could cause this problem due to the build up of carbon (coking) in and around the throttle valve. You would probably need to have that diagnosed and maybe replaced if proven faulty.
Checking the fuel pressure would be the next check. Fuel pressure should be about 52 to 58 psi.
There is a service bulletin on a engine stall and rough idle pertaining to the fuel module strainer inside the fuel tank being clogged and would need to be replaced. The service bulletin is listed below.
File In Section: 06 - Engine/Propulsion System
Bulletin No.: 00-06-04-044
Date: October, 2000
Engine Hesitates, Stalls and/or Will Not Start
(Replace Modular Fuel Sender Strainer)
2000 Chevrolet Cavalier, Malibu
2000 Oldsmobile Alero
2000 Pontiac Grand Am, Sunfire
Condition: Some customers may comment that the vehicle engine hesitates, stalls and/or will not start.
Cause: This condition may be caused by a restricted or plugged in-tank modular fuel sender strainer.
Correction: Replace the existing modular fuel sender strainer with a new strainer, P/N 88891094. To insure correct installation, follow the instruction sheet contained in the service kit. Also, refer to the service procedure found in the Engine Controls sub-section of the Service Manual.
This service bulletin is supplied by the Alldata automotive information website.