Question about 1999 Pontiac Grand Prix

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Car has no power and has a rattling noise

It started with engine code telling me that I have a cyclinger 1 misfire. I cleared it but it would come on when my RPM's would hit 4000. I changed the spark plugs, wires, fuel filter, air filter but I still have the orginal problem that the car looses power at 3- 4000 rpm. I can drive it 120 miles and hour at 2500 RPM and the power is there but as soon as I s stomp on it, it makes a weird noise and does not accelerate.

OK, car gave up yesterday and now has now power whats so ever. It has a rattle in the engine or back of engine where exhaust hooks up but it is tuff to pin point exact location. Car will only go about 40 km per hour.
Thanks for your help

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RPM and speed do not match what I'd expect to see at 120. but that could be gear ratio being different than I'd expect. Most don't like to run at 4k. Most problems at that rpm is either plugs (experiment with different gap settings or change heat range one step colder or hotter) or can be coil related (work fine except when recovery time is shortened due to rpm). However, the weird noise may be due to a partially plugged catalytic converter. So, check that as well. If you have a knock sensor, test that too.

Posted on Oct 05, 2009


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