I'm working on my brothers '90 Iroc, trying to fix the backfiring problem it has. It backfires during deceleration through the exhaust @ like 3,000 rpm and higher. Any ideas @ what the problem can be? Any suggestions? I've already checked the timing, valves, timing chain,(all were good) and are in need of help. Thanks....

 

is it running rich?

 

I haven't checked that. Any ideas on how to check if it is running rich? Thanks

 

All the plug wires are good, and they're on the right plugs?

Perhaps one of the injectors is bad? Do an ohms test on each injector. They should be greater than 12 ohms, preferably 16 ohms.

 

Mine backfired until I got an adjustable fuel pressure reg. Fixed it up good but I may have been a rare case. Hard to believe fuel pressure would matter.