What are signs of a bad ignition coil? My 92 cam has been running kinda off lately...everything had been pretty much replaced and I did teh basic tune up. Sometimes the rpms would climb up really slow then backfire and then other times it'll run normal. It keeps changing even if I've been on the road for awhile. I also noticed my gas mileage sucks too.....I swear man, I think my camry has PMS or something.