i have a 1997 CHEVY CAMERO 3.8L, auto, when the car get hot the car startes to act funny, the Rpm starts bouncing around, (note the engine is ideling funny also when this happens , so its not just the cluster) this only happend this summer, it never happend in the winter. i took it to the GM dealer and they couldnt diagnose it, they were leanning toward the ignition coil, but werent sure, so i took it back from them and i replaced a ignition coils (all 3) with a known good one(all 3) still the same problem.... recently i replaced the catylitic converter because it was plugged, and the car kind of runs rich.. so i am totally lost here not to sure whats up with my car.... did anyone have a similair problem? or does anyone have a clue what it could be? the car has no falut codes... and this problem is intermitten. If anyone can help that would be great, thanx

 

Make sure the O2 sensor is working properly. Test it with a scan tool.

 

had a simialr problem in my 99, might be the plug wires, they get hot...and dont work worth a crap, did some research,replace the plug wires, wrap the wires with heat tape from MSD, works really well, common problem I hear, good luck

 

easy way to tell bad plug wires is to spray them with water and see if the car runs different. your problem seems different. it could be your MAP or MAF (not sure which one your car has)sensor if the car is surging.

where you said you just changed a plugged converter, Z28pete is right, it could be your o2 sensor. also an often overlooked sensor is the coolant sensor. it has a tendency to go bad along with the o2 sensor. usually though when these sensors go bad, along with the plugged converter, you usually experience a loss of power along with a rough running engine