hello I have a 99 pontiac grand prix

Asked by Mar 22, 2017 at 09:42 PM about the 1999 Pontiac Grand Prix 2 Dr GT Coupe

Question type: Maintenance & Repair

my 99 has been running rough for some time now, has service engine soon
light flashing most of the time when i drive it but occasionally will just stay on.  
I've replaced the spark plugs, wires, coils, fuel pump, and fuel fuses and still
runs ruff most of the time i drive it. anyone with good advice can you help me
out???

1 Answer

75,785

First thing is have the computer scanned for trouble codes. Most auto parts stores will do it for free. A flashing service engine soon light is warning you that the engine is misfiring and damaging the catalytic converter. It could be a number of things. Bad fuel injector(s), MAF sensor, faulty EGR valve, leaking intake manifold gaskets, faulty crankshaft sensor, etc. We'll need the trouble codes to see what's going on.

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