I have a 93 Grand prix and my mpg has gone from about 22 mpg to around 15~16 ish the car isn't as quick as it once was their is no soot or anything at the exhaust tips. The O2 sensor is a year old and has about 12,000 miles on it the air filter is okay the fuel filter is okay I checked the spark plug gap and its fine. My car has the 3.1L MPFI engine it has the digital EGR valve with the three solenoids how do I test the solenoids to see if they are working and should I change the PCV valve as well?. the grommet is new but the valve is the original. I run 87 oct in the car the engine does not have anything wrong with it mechanically and the fuel injectors are working as they should the engine doesn't stumble or miss.How do you check to see if the EGR valve is working?.?
It sure sounds its the EGR valve. You might wanna clean it out first with good carberator cleaner and replace the gasket. Do replace the PCV and also check your MAP sensor.
One more thing. Does your car hesitates to start the first time? Does the RPM bounces on stops or idle? Or does it jerk forward while driving like a slight gas rush into the motor? If so then do replace the EGR. Have it checked at a shop if you have doubts.How do you check to see if the EGR valve is working?.?
try some injector cleaner even though it doesnt stumble the injectors still might get a little bit clogged with todays gas additives might try some octane boost it worked for me
