Just for the record, I did search through some threads about possible opti problems but couldn't find anyone with exact symptyms I am having.

2 weeks ago I started to get a misfire but it wasn't bad. Recentely it got alittle worse. When the car is cold it doesn't really give me any problems but when it has been warm for a while it starts to give me problems. The thing is these problems don't happen all the time. Today I drove to a dealership to look at an Audi A4 and the car didn't give me a problems the whole way there. It probably took 1/2 hour to get there. On the way home I stopped at the mall and I didn't have a problem either. Then on my way home from the mall it started to act up. It started to bog alittle, then it backfired really loud (never had that happen before).

Now does this sound like a problem with the opti? My plan is to replace the opti as well as plugs and wires and hopefully that will fix the problem. Could a fuel pump have the same characteristics as an opti when it is going bad?

BTW: car has 120k miles. What is normal fuel pressure for idle and thru the RPM range on a stock car?

 

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The backfire is too much fuel in the exhaust and not enough spark. I doubt its the fuel pump and I doubt its the opti. I've gone through 4 optis and when they start to go they are usually bad all the time.

If its only happening when the car is hot I would look at the coil or ICM. Have you done the ICM cooling mod? Put two fat washers or nuts between the head and the coil bracket.

 

Im going through a similar ordeal right now and I've replaced plugs, wires, coil, tested it with a new ICM, checked fuel pressure and changed o2s, still no having the same problem. Good luck brother.