Well Ive had my ZC for 5 months now, and it has intake, exhaust w/ gutted cat and no resinator, and an ls ecu. It back fires while down shifting some times, and also when I let off the gas at high rpms. I think it is the ecu making it back fire, but was wondering if you guys had any ideas. It doesnt run bad at all, and is very quick, but its kinda annoying(almost sounds like a gun going off). thanx

 

If its the popping noise you are talking about mine did that to I had a 2.25 in exhaust with out a resonator and every time i got on the gas then got off and back on it would (pop)backfire.So i took it to my shop because i was stomped the timing was right everything was fine.I talked to a couple of guys and they all says its the nature of the beast which means its going to do that do to back pressure(not enough or to much).Hope this helps.Your car is fine.Just put a resonater on like i did it quiets the popping down alot.

 

so the resinator wont hurt the performance at all. If not Ill do it tomorrow, thanx.

 

Get a CAT in there. Gutted cat on a ZC kills performance in my opinion, and may or may not account for fuel igniting in the exhaust (probably unrelated though). I have no dyno info to show the gutted cat being bad, but my experiences were that it made my ZC feel sloooooowww until I replaced it. Its only a ZC, it doesn't need 2 1/4" of almost totally unrestricted exhaust.

It probably mostly due to the ecu running it a little rich. The resonator mentioned above is most likely just drowning out the sound of the backfire. The teg ECU isn't perfect for the ZC, so I'd imagine that the back firing is just going to be a fact of life. You can try to quiet it a little with the resonator.

Mine backfired really badly for a while, then I turbocharged it. That seems to have eliminated the problem. Its just a suggestion.

 

Any exhaust leaks could cause it to back fire also.....

 

Thanx for the replies, I will probably just put a hi flow cat and resinator on in a little bit. Oh and by slow what do you mean, did it make that much of a diff.

 

Its called lack of back pressure. Get a cat and it will stop.

 

The cat broke apart inside, so I gutted it. I took the car out for a spin and it just had no low end power at all. The lack of back pressure reminded me of someone pedaling a bike with no chain on it. Its hard to explain, but it just didn't run well at all. I found a cat right away, and it felt much better again.