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Ask GM Tech (Cam) Your Own Question
GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 29431
Experience:  GM Grand Master Technician 2007. 14 years experience.
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2004 chevy impala: p300..multiple random misfire..skips

Customer Question

2004 chevy impala p0300 multiple random misfire replace plugs car still skips and the check enginge light blinks
Submitted: 5 years ago.
Category: Chevy
Expert:  GM Tech (Cam) replied 5 years ago.

GM Tech (Cam) :

Hello, I'm Cam. Please include all the details about your issue so I can accurately advise you. I cannot see your vehicle so please be detailed.

GM Tech (Cam) :

There are 2 possible and very likely causes for this. First is the fuel pump. If the filter was plugged, it could have caused premature wear on the pump and the lower fuel pressure as a result.

The second possible and even more likely cause is a plugged converter. These engines are notorious for the catalytic converter plugging up. It will set the Mass Air Flow sensor code because the engine is not breathing correctly. I would start with a back pressure test. This is done be taking the front oxygen sensor out and installing a gauge in there to see what back pressure there is from the cat. There should not be more than 1psi at the most.

Expert:  GM Tech (Cam) replied 5 years ago.
There are 2 possible and very likely causes for this. First is the fuel pump. If the filter was plugged, it could have caused premature wear on the pump and the lower fuel pressure as a result.

The second possible and even more likely cause is a plugged converter. These engines are notorious for the catalytic converter plugging up. It will set the Mass Air Flow sensor code because the engine is not breathing correctly. I would start with a back pressure test. This is done be taking the front oxygen sensor out and installing a gauge in there to see what back pressure there is from the cat. There should not be more than 1psi at the most.