Help needed! Engine running rough after header install.
Help needed! Engine running rough after header install. I have a 98 C5 vette. I just installed headers on it. After the install I started up the engine and now it seems to be missfiring. It doesn't run too bad at idle but when you put a load on the engine it shakes and backfires. I left the cats and O2 sensors on it. It is throwing a code for low voltage in once of the O2 sensors. But I took it to a corvette specialties place here in Tulsa and they said that the sensor wasn't the problem but after hours and hours of diagnostic testing they told me to just take it to the dealer. I have searched ls1 forum and corvette forum for the answer to my problem but I haven't found anyone who has ever had this problem before and no one on corvette forum will help. If anyone has any information or any ideas on this problem please let me know. Thank you.
im not a mechanic but things i would check would be all the plugs and wires make sure they are the right ones and make sure they are all in ok. maybe you need a tune. i dunno im sure someone who know will be here soon
ok im thinking this is the 02 sensor prob. has your gas mileage seem to have dropped?? with it just running or can you not even drive it? but the guys at the dealership prob just didnt want to deal with your prob. check the wires that run from the o2 sensors to the lil ecm box under the hood make sure they are not burnt from the headers that is a high possibility. or either the o2 sensors have just went bad. that is really the only thing that i can think would be wrong with it.
It seems like it's drinking more gas than usual. It doesn't seem bad at idle. You can hear it kind of missing or something. It sometimes will make a loud pop/ backfire when you start the car. It only shakes really bad and backfires when the car is under a load, (like getting on the highway).
ya do what i said in my 1st post check the wires make sure they are not burnt or anything but that is the symptoms of a bad o2 sensor. just go ahead and replace them anyway it will be ove $100 but i believe it will fix it.
ok you can run o2 sims for the rear o2s, but in the front you have to have o2s. but you dont have to have a tune but the ses light will be on. Im talking about your front o2s are bad or the wires have been melted. But in order to get the ses light off you will have to get somebody with HPtuners or a similar tuning device to delete the rear o2s. but 95% sure your o2s are bad.
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Did you pull the plugs, and put new plugs in during the swap?
If so, or even if not, you probably need to check that you didn't crack the
ceramic on any of the plugs. Pulling out my old plugs I busted the
ceramic housings on 3 plugs on my second header install.
Also did you disconnect the main wiring harness on one side, pass side? and
forget to plug it back up. I did that on my first header install.
The only other think I can think of is there's a vaccum leak after the MAF
meter. Did you take any of the intake track apart? Even if you didn't check
that everything is clamped tight and not causing a vaccum leak like from
the AIR or EGR fittings.
If so, or even if not, you probably need to check that you didn't crack the
ceramic on any of the plugs. Pulling out my old plugs I busted the
ceramic housings on 3 plugs on my second header install.
Also did you disconnect the main wiring harness on one side, pass side? and
forget to plug it back up. I did that on my first header install.
The only other think I can think of is there's a vaccum leak after the MAF
meter. Did you take any of the intake track apart? Even if you didn't check
that everything is clamped tight and not causing a vaccum leak like from
the AIR or EGR fittings.
Ok, I checked the spark pulgs and they are fine. Thay are also getting spark so I know the coil packs and wires are working. The map sensor code spawned from the idiots at the corvette shop not plugging in the map sensor behind the plenum. I don't know where to go from here. The only codes I have now are the air system code b/c of not having the air runners on the headers and the engine speed output circuit b/c of the tach not working. Any ideas what to do or look for now? Should I have it tuned or buy a tuner and see what happens? I hate to blow $300 and it not help.
Oh, and I didn't find any vacuum leaks. I fixed the one it had to the map sensor but no dice on it fixing my problem. Also I never disconnected the wiring harness, I didn't have to to get the headers on.
On The Tree
Joined: Feb 2006
Posts: 107
Likes: 0
sounds like a 02 sensor problem, i would try replacing them, when i did the long tube install on my Trans Am it was doing the same thing, also check for any leaks o2's will not work correctly when theres oxygen getting into the exhaust system.
Teching In
Joined: Feb 2005
Posts: 19
Likes: 0
From: canton, MI
Yeah..I would check into the O2 sensors. Change the O2 sensor thats throwing the code, or put eliminators in place of the downstream O2's. I wouldnt buy a tuner or have it tuned, because there is a problem that needs to be corrected and a tuner/tune wont do it for you. A set of headers on a LS1 should not cause major problems. Especially if you have cats and all your O2 sensors still on it. I also wouldnt take it to a dealership. They more often than none dont know what they are talking about when it comes to aftermarket products on cars. You'll end up walking out of there paying for some jackass to walk around your car scrating his head and not being able to correct the problem.
Last edited by Anti-Venom; Sep 25, 2006 at 12:54 AM.
Sounds like the classic sign of a cracked plug. I'd throw a fresh set of NGK TR-55's gapped at .055.
Did you install the headers with the plugs still in?
Also, make SURE you have the front O2's plugged into the FRONT O2 harness. I would trace out the wires if they are plugged in correctly and make sure nothing is burned/shorting out.
If you end up needing O2 sensors, search posts I've made about Bosch 13111 sensors and throw a set of those in. I've posted a link (recently) on where to get them cheap, but I'm too lazy to find it.
The REAR O2 sensors will have no affect on how the car runs whatsoever (plugged in, not plugged in, simulator plugged in, etc.)
Did you install the headers with the plugs still in?
Also, make SURE you have the front O2's plugged into the FRONT O2 harness. I would trace out the wires if they are plugged in correctly and make sure nothing is burned/shorting out.
If you end up needing O2 sensors, search posts I've made about Bosch 13111 sensors and throw a set of those in. I've posted a link (recently) on where to get them cheap, but I'm too lazy to find it.
The REAR O2 sensors will have no affect on how the car runs whatsoever (plugged in, not plugged in, simulator plugged in, etc.)