Last year my car started to misfire. It would run fine all day until I would put it under a load then it would start to misfire. After it would start to misfire it would not stop misfireing untill the car had completely cooled down then it would run good until the next time I put it under a load. It would misfire at all rpm's even under part throttle. About two week ago I replaced my coil with a MSD coil and the misfire went away completely. My car started to misfire again two days ago and know it starts to misfire even when the car is cold(from idle all the way to 6000 rpm's). Is it posible that my new MSD coil craped out already? Could it have fried my opti (I have heard it could and I hurd it was a rumer)? I know that it is not my wires or plugs. Can someone help?

 

It sounds like the opti is craping out . But are you getting a SES light.

 

It sounds like you may have a burnt wire arcing. Any stored codes? Did you check fuel pressure?

 

I use to get a code before and know it won't throw one. I know that it isn't the wires because I changed them after it started to misfire and I installed fire protectors. I haven't checked fuel pressure yet. Also when it misfires it is not cylinder specific. It will misfire on all cylinders.

 

sounds like an opti to me.

 

I'm having the same problem working on my cousins car right now. It has a new coil on it also...i've tried everything except changing the opti and the damn thing still has a dead miss on #6 cylinder. I dont guess my cousin or me can complain to much though cuz its the original opti with over 140k on it.......and its a non vented one at that.

 

I am having the same problem with mine, once it gets warm I give it half throttle it back fires through the exhaust and Mis-fires bad. I was thinking it was a O2 sensor. I am getting no codes either. Please help

 

Does anyone know if the rumer about the MSD coils frying the opti is true or not

 

No its not true , but its not so much about the coil as its about an aftermarket ignition box i.e. 6AL MSD or whatever and even with that there are guys that haven't had any problems with there's.

 

Hey for what it's worth...

I had a misfire problem with my LS1. I thought I had replaced my plugs when I did my header swap. When I got on the throttle hard, the misfire came alive and it was quite embarassing. When driving regular I had no misfires. I changed the plugs yesterday and she is like new... never missing a beat. I don't want to underestimate your trouble shooting, but I didn't think anything about my plugs at first... I immediately thought I should have my PCM adjusted for all the mods. Not so. Hope this helps if you didn't replace the plugs yet.

Good luck.