I recently installed a set of MAC headers and an offroad y-pipe on my friends 01 camaro SS. The car runs and sounds great, but there is one problem. Under a load or when you get intot he throttle, it will make a back-fire sound and flash and SES code just for a second, then the code will go away, but he car will run poorly and idle really low...around 450-500 RPMs. if you shut the car off and start it back up, it will run fine for a few more minutes, then eventually the problem will occur again. I have checked the O2 sensors, all teh wire connections i dealt with, and everything else that i could think of that may cause the problem, but it still does it. I have tried runing it with the o2 sims and with the regular rear o2 sensors and it made no difference. HE just bought he car a week ago so i dont know if it wsa something that i did witht he install or if something is wrong with the car itself so he took it to the dealer today and they said there wsa no codes thrown in the memory bank on the computer. their explanation for the problem was that there was not enough backflow, causing it to backfire...which i think is wrong becuae i run open headers all the time with no problems. does anyone know what could be causing this problem or what i could check? I also put in AC delco Iridium spark plugs during the header install too. any help will be appreciated
Chad

 

did u reset the pcm?

 

No i didnt reset the pcm...i never unhooked teh battery cables when i worked on it. Think that would cause this problem? I drove it some more today and foujd a few otehr things....it always starts fine but when you get on it at WPT or close to it and shift from 1-2 or 3-4 it will backfire, show an SES l;ight for a second. It will run fine after the backfire, but just idle really low at a stop. Then once you get on it again it will pop and do the same thing over again. again no codes are thrown and it will idle fine after you shut the key off and start it back up. I will try to reset the computer when my friend gets off work tonight, hopefullly that will do it, i should've thought of that before now. any other suggestions just in case this doesnt work? thanks for the reply

Chad

 

Aren't the O2 sims supposed to go on the rear sensors? The front sensors are supposed to be left alone. All the back sensors do is measure catalytic converter output to test for a defective one, the front O2 sensors are the ones that matter to the computer and the running of the engine.

 

yeah you are right, sorry i wasnt very clear on that. i have the front o2's hooked up, but what i tried wsa hooking the o2 simms to the back o2 wire connections, then i hooked up teh factory o2 sensors onto the back wire connectors....trying to rule out a bad o2 simulator. It acted teh same way both ways so i put the o2 simms back on the car on the rear connectors. any other suggestions? Thanks