hi i have a 97 ta and im getting the radom multi cylinder misfire code .here is what ive done, ive replaced the opti spark with new gm part,iver replaced the plugs with ngks ive relaced the plug wires with taylors and ive replaced the coil with a new gm part.and i still have a bad miss it seems to be worse in higher rpms like when i rev it up and let off most the time i get a loud pop also.another thing im goin to replace in a few min is the coil wire it seems to fit to loose on the coiil so im gonna try that and see what that does.if this does not fix my problem what could it be?i also thought maby it could be my loud mouth exhaust and the lt1 knock module so i even replaced that with an lt4 module,and still nothing any better HELP!!!!!!!(i checked about 10 times to make sure i didnt have a plug wire crosed also.

 

did you replace the whole opti? or just the cap/rotor....

 

i replaced the whole opti!!

 

Do you have headers? I had the same thing, so i replaced my wires, and it cleared up for like an hour, then started doing it again. Turns out the way the headers fit on my car, the number 6 wire was very close to the header, and had to be run around the back of the oil dipstick to avoid touching it. Also ran accel shorty plugs and haven't had a problem since then.

 

i have edelbrock shorties goin into slp loud mouth system. which i must say i hate it .sounds like crap up high it sounds pretty good at idel, i think alot of the sound i dont like is the missfire though .also the headers are junk too the plug access is horrible but anyway ive made sure the wires arnt touching the headers and my care hasnt even changed and ive replaced everything i can think of .so what should i do next?

 

Are you getting this popping sound from the exhaust only when you rev it up and let off the throttle?

 

yes its when i let off of it.and not talking about like a lil pop and i know some of its normal ,but its honestly sounds like a gun going off and it also missing going doen the road mostly at higher rps,but some lower too .any ideas

 

That code can also be the result of a fuel problem or vacuum leak. How long since you did a fuel injection cleaning and fuel filter? Also check the fuel pressure at idle and at WOT.

 

I would also suggest a fuel filter and a check of the fuel pressure.

 

I had this problem almost exactly 1 year ago. I had just finished the heads/cam swap. The setup is so mild I didn't not do much tuning.

Turns out it was running so rich at idle and low rpms it was washing out the spark setting the P0300 code. I increased the injector constant and leaned it out a bunch and it was fine.

In the last couple of months it's started doing it again and I can't figure out out. I was running a bit rich again (i've changed injectors since then), but not nearly as rich as the first time. Still, I leaned it back out and I am still getting the code. I also put new plug wires on as well.

You can feel a hesitation/stumble at idle, and if you hold the car at 2000 rpm you can feel it there too. I am beginning to suspect my 1.5 yr old, 13,000 mile Optispark.