possible air check valve
 

well when my stock muffler was installed i never noticed this, but when i installed my flowmaster during cold starts when i rev or release the gas to shift theres a loud pop from the exhaust. its loud and tingy.

i asked one of the experienced techs at work and he said its probably something from the emissions equipment. i did a few tests this morning.

i started the car cold and revved it. it did it. i removed the air pump relay and started the car again. i did not hear the smog pump and when i revved it, i could get it all the way to 5 grand and when i let go it didnt have the slightest bit of pop.

this tells me its in the smog pump circuit, and my only guess of how it could interfere with exhaust pressure would be the check valves. i unplugged the air hose from the pump side of the check valve on both manifolds and had both audible and physical evidence of exhaust flow.

arent these are supposed to be one-way valves? does this mean my check valves are bad?

good luck figuring that out, when it comes to emissions i get confused

I had the same problems with my car when I first had, I solved it by removing it all...too bad you live in Cali!! haha

You should be able to check by blowing thru one side and not being able to on the other, thats a simple check.

Mine exhaust still pops now and then but I think its from my overly rich running motor..

yeah i read on cz28 that its normal on cold start cuz it runs rich and theres just unburned fuel igniting in the exhaust.

Most of the time if it does it cold dealers will even tell you it's normal

my car does that in cold also, i think its pretty normal