I just got finished putting on Pacesetter LT's with a custom Off-Road Y-pipe and on the ride home from the exhaust shop the car was backfiring a lot in the upper RPM range. Also seem sto be running VERY rich. I have not got my O2 sims in yet, but I do not know if this could be the cause. The car idles fine and accelerates fine, but when you really get into it it starts running badly. Any Ideas?

The O2 sims should be in next week, but I need to know if I shold be looking at something else.

Also, it seems that the Air Check valves are chattering alot since the install do I need to block or modify them?

TIA

 

I wouldn't drive it until you get those simms in. I bet this is the cause of all your problems cause your PCM is like

 

your car is in "limp home" mode. its normal. get your simms in and reset the PCM, you should be good to go

 

Well I got the simms an installed them, disconnected the battery for 10 mins and pulled the ecm fuse. Still have a service engine soon light and the car is still backfiring.

any other ideas of what it could be?

 

check the front O2 sensors. Make sure they are all the way in. Also check all air hookups, and be sure wires are not arcing out.

 

still have EGT? any leaks?

as he said, check all plug wires at the plug and the coil

 

Another vote for a close inspection of all the plug wires. My friend installed a set of LT's and melted a couple of wires. He ended up putting those nomex/kevlar sleeves over the wires to keep from melting them again.

 

Could also be a cracked plug (if you accidently whacked one during the install or something.)

 

It's not the rear O2s. I drove around for a few months with the rear O2s unplugged...no problems except for the SES light.

As said, check the front O2s and plug wires.

 

Yeah let's get this straight right now.
REAR O2s have nothing to do with the way that the car runs. They report to the computer whether the Cats are working or not. If not it just sets a code to let you know that something is wrong. It does not change any of the computer settings at all.

Pull that code and see what it is. As stated by others check: plugs, wires, and O2 wires.

 

I hope I dont' run into problems like you guys are. I just got finished installing my LT's today it took about a week to do because of limited time etc. I started it up and it started great, the #5 and 6 plug wires seem to be melting a little bit. Can anyone link me to these nomax/kevlar sleeves you were talking about?

Is backfiring that bad, all mine does is pops.. If it is what causes it? I just redid my whole plugs and I still have some backfire, some people tell me that it's not normal. How can I tell if one of the plug wires is completely melted? My car seems fine at high RPMs and at idle etc.

 

After getting the headers, y-pipe, and high flow cat installed do you have to get the car dyno tuned or use a programer?

 

i had the same problems, i found both times it was a spark plug boot came off the plug.. got all sorts of error codes and car backfired and ran like crap.. so i lifted it up checked and reinstalled the boot and good to go again

 

you don't need to reprogram anything after headers. a tune will help in any situation, but there is nothing about a header install that mandates a tune.

i don't know what those goofballs were saying about not driving without sims...the rear o2 sensors have no relevance to the running condition of the car. they only trigger the SES light as a warning that the cats are not functioning properly. i drove with no sims for over a year without problems.

one thing to remember is that if you pulled the battery on the car, the volitile memory in the computer was erased. that means it has to "relearn" alot of the info. that can take up to 200miles of driving so i'm told.

so if it's running strange, double check your plugs and make sure you aren't getting any exhaust leaks. a leak can throw off your o2 reading alot and cause problems. then just let the car adjust itself for a while and see if it gets better.