QuestionHello, this question is relating to a 1997 Corolla 1.6L that started misfiring a few weeks ago. So far, I have changed the distributor cap, rotor, wires, plugs, fuel filter and got the injectors cleaned. The O2 sensor has passed and so did the coil pack - no problem there.
It runs great the first 15 minutes or so when the engine is still cold ... but then it starts to misfire after the engine is warm. Right when the car exceeds 60mph, it starts doing it. I am at a loss as to what to check now. I ve had a mechanic spend 3 days diagnosic the car and all he has found is that it runs too lean sometimes but he can't tell why. ANy help would be appreciated ... this problem is really getting to me!
AnswerI assume that the engine idles normally, it sounds like the misfire is rpm related and it misses at higher rpm, road speed has little to do with it but rather the load on the engine and the rpm.
If the engine should run too lean even at times the check engine light should have come on, was this the case?
If so I need to know what the trouble codes were in order to be of more help. There are a couple of possible trouble areas, the mass air flow sensor or maybe a fuel injector that is sticking at higher speeds or it's simply losing fuel pressure. Unless the mechanic has already done so I would suggest connecting a fuel pressure gauge so the fuel pressure can be monitored while driving.
