I changed my plug wires last week, removing the stock wires for MSD 8.5mm. I have checked and double checked that the wires are connected to the correct terminals on the opti. I'm finding that the car is misfiring or backfiring and you can smell fuel when under the hood. When coming off the throttle the engine makes a sputtering noise (almost like an exhaust leak). When on the throttle, the car is running smooth (no knocking feeling) but there sounds like a 'backfire' or 'misfire' under the hood. Any suggestions before I hand this thing over to a mechanic????

 

After my header install, I had the same problem but we had two wires crossed. I know that you said you have checked this but the symptoms are the very same. Have you checked under the hood at night (in the dark) for arching of the wires? Just a thought.... Good luck with finding the culprit.

 

I'm having a similar problem. When I let off the gas, I get 1 or 2 backfires everytime as the car decelerates in gear. Runs fine otherwise. It must be running rich or something when it does it cuz the exhaust starts to smell like fuel. All new opti, plugs, and wires which I verifiyed to be good. Everything is installed correctly. Any ideas? Would bad O2s cause backfires?

 

Cmon, I still could use some help!
I disconnected my O2's and I'll see if it does anything.