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1998 Pontiac Sunfire, codes 0172 and 0404. I have replaced the egr valve and the o2 sensor, driven several hundred miles. The same codes keep returning? This egr valve is the all in one version. Help?
Bill
I’d be looking more at the P0172 code for starters. That code means that you’re running rich, which is either due to a lack of airflow into the engine or extra fuel being delivered into the mixture. Check to make sure the AIR FILTER is clean, and there are no blockages in the intake path.
I’d recommend checking fuel pressure to see if it’s in spec, and if possible do an injector balance test to see if one or more injectors might be stuck open and putting too much fuel in the mixture. Check for any fuel leaks that may be getting into the system as well, such as a leaking fuel pressure regulator. As for the P0404, that is an EGR open position performance code.
If you’ve replaced the EGR with an aftermarket unit, I’d recommend using a GM part. Otherwise check the wiring to the valve for any problems. There could be an updated PCM calibration for that particular problem, but you’d have to check with your local dealership for that. Possibly a bad PCM as well, but that requires a lot more checking. Good Luck!
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