The PCM (computer) is like a weatherman. It's right 50% of the time.
I would start with the basics - pretend you're working on a '57 Chevy or something - no computer.
1. Check for vacuum leaks.
2. Check for any other obvious (or not-so-obvious) problems, no matter how small or insignificant.
Now, we look at cause and effect. If you have any actual symptoms, make a note of the symptoms and driving conditions. For instance, are there any funny noises, smells, etc? If there are no actual symptoms, then you can start to look at why you're running too rich.
Are you idling too high? If so, then it could be the idle air control valve. However, if you're idling around 700 RPM, then that's probably not the cause.
The oxygen sensors set their own specific codes when they go bad, so unless there are other codes, I would not worry about them.
The mass airflow sensor is a possible cause, because if it goes bad, it could cause the computer to think there's not too much air, thereby richening the mix.
If these don't do it, then you could take it to the dealer and just run a diagnostic, no repairs, since the car is drivable. They'll charge about $100 to give you the answer, then you decide whether you can do it or not.
Wednesday, September 26th, 2007 AT 7:41 AM