After getting the intake manifold gasket replaced on my 2001 Grand Prix a few months ago (and shoftly after that, a new catalytic converter), it started doing this; it will dip to under 1000 RPM, as normal for idle, but then it loops back and forth between roughly 600 and 900. As far as I can tell, the engine behaves normally at cruising speeds, both on side streets and the freeway. Last Monday, it started showing the oil pressure light, indicating the pressure's "dangerously low", but I'm taking it to a nearby mechanic tomorrow to have them diagnose THAT issue. I was told after the manifold gasket replacement that it's running rich, which doesn't explain why, after running rich all winter before carbonizing the catalytic converter (forcing me to replace it), it's suddenly causing this problem at idle. The trouble codes I'm getting are as follows: P0171 (System Too Lean; Bank 1) (this one was actually displayed TWICE when I scanned the system); and P0300 (Random Misfire Detected).
have the same problem?
Sunday, June 15th, 2014 AT 4:28 PM