My 1999 Grand Am GT misfired on cylinder #1 at high RPM. The car runs great, but the engine light is on and it feels like it's missing power at higher RPM. What could be wrong?
by 
KiwiBanks
ANSWERS: 4
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First thing I would do is a compression test on all cylinders and pay psecial attention to the #1 Cylinder. Then I would check very closely for either oil in the coolant or coolant in the oil. I had the very same symptoms in my 98 Grand Am - intermittent missfire, check engine light codes that said replace MAP sensor. Turned out to be a head gasket about to blow, which it eventually did. OUCH! said I as I wrote the check for $2500 to the Chevy dealer in a little town 200 miles away.
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have your coil checked. you may have one that is slghtly weak that ill give out at high rpm's. not sure of your exact setup but you may have 1 coil per cylinder as some cars do.
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The very first thing you need to do is read the code that is tripping the Check Engine light. With that code we can move forward diagnosing the problem. If we just guess you can spend hundreds of dollars unnecessarily. Take the car to a parts store and they will read the code for you if you don't have a code reader.
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Pull the plugs (not just cyl 1 and check their condition. They may be worn out, or fowled. If the plugs are good, then check the spark plug wires, make sure they're intact, not corroded, and snapping on good. If they are good, you may need a fuel system cleaning. It may just be a clogged fuel filter, or clogged fuel injector. You can try a cleaning additive.
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