My car (94 T/A, A-4, all stock) runs great when it's cool. But once up to normal operating temp (220 deg), it backfires through the exhaust at higher RPM. It's fine up to about 5000 RPM, but right before the 2-3 upshift, it sputters and backfires. Once the shift is made and the RPMs are down, it runs great.

Any suggestions?

Thanks,

Finn

 

Mine used to do this when my opti was gonna take a crap, till one day it backfired and stalled. After a tow home and a couple of hours to change out the opti all was perfect!

 

Had the same problem 2 years ago, high RPM backfire, lived with it for a while.. told myself just dont run it high RPM but it finally started to bother me, why own this car if you cant use all of its performance potential. Car wasnt setting any codes, fuel pressure was fine, drove it with fuel pressure gage connected. Plug wires were only 10k miles old. Replaced opti, no help. Ran car at night to look for sparks from plug wires none... Drove down the highway at 60 mph in 6th gear and accelerated in 6th gear trying to load up engine to make it miss fire, ran fine.. At this point was totally confused . Went ahead and bought new plug wires even though wires on car pretty new. Installed new wires, problem fixed.... thats my story. Your case may be as simple as a coil wire, a coil, or plug wires. Good luck.

 

Try doing to the washer mod on the ICM on the driverside head. And put a damn 160º thermo in that. My car never reaches 220º.

 

Thanks to all for the input.

The Opti is fairly new (for whatever that's worth) and I've done the washer thingy. Don't know when car last had the plugs and / or wires changed. I've been putting that off, but I guess it's time...

Thanks again.

Finn

Edit: Oh yeah, I got the 160 deg therm but haven't rigged up a fan switch yet.

 

Ok im feeling dumb... whats the trick with the washer????

 

This trick with the washer...

http://shbox.com/1/4th_gen_tech2.html#ICM_cooling

It doesn't seem to have helped me, but it probably didn't hurt and the price was right.

Finn