General Maintenance & Repairs - Misfire? Post Header Install...

I know this topic has been beaten to death; I've been back through about a 1000 posts related to misfires and backfires. No one seems to have exactly the same problem as me.

Here's my problem: My car develops a backfire under acceleration anywhere from 50% to 100% throttle. It also seems to lose power a bit when this is going on, but it will pick up again and seems to really run hard right up to 5,500 when you get by the "backfiring" stage. A really good way to get it to do it is to pull out of a stop on a slight uphill, then pretty quickly feed in 50 to 75% throttle. It will do it when it is not yet warmed up, or when it is warmed up. You will hear a stuttering/growling/backfiring sound from behind the driver and it will hesitate a bit, then take off. If you roll onto the throttle real gently, you can feed it in all the way to WOT and it will run fine. It will not do anything strange if you are riding along at 60 or 70 in 5th or 6th and floor it under a load. It occurs pretty much exclusively in 1st under a load, and you might get a few pops if you run it really hard through 2nd.

All the plug wires are tight on both sides. I replaced one plug wire that was touching the AIR tube that I thought was the culprit. That didn't fix it. I also replaced that plug, and that didn't fix it. I don't know how to test the resistance of the plug wires, but if somebody would help me out with that I would try it. I am not a mechanic, but I have brought the car to 2 different mechanics that had scanning capabilities and both told me nothing was wrong with the car. I know that's not true; I drove the car for about 200 miles after the header install and did not experience this problem at all. It also never sounded like this before the headers.

My recent mods include a TSP lid, Pacesetter LTs, Pacesetter ORY, Magnaflow Catback. The AIR and EGR are still in place. The AIR intake tube has a crankcase breather filter stuck on it since the TSP lid had no place for it. Other than that the car is stock, and has 24,000 miles on it. Thank you for your help.

If you drove for 200 miles before this started, it's more than likely a burnt wire. The coolant temp sensor on the driverside head, in between the header tubes in the front could cause this as well.

If your sure all the coils, plugs , wires, and the main harness for the coil packs are secure/plugged in tight it could also be a broke ground wire on the back of the heads or from the block could cause it as well.

I'm thinking coolant temp sensor or burnt wire somewhere though.

I dont understand. Why do you say coolant temp sensor wire? How would that cause problems.

To check for a plug wire arcing - start the car and rev it - in the dark.

As said above, check for maybe wire arcing to ground. Park somewhere dark and open the hood. Look for any arcing to grounds from the plug wires. If you dont see any, grab a spray bottle with water in it and spray the plug wires. This will usually show the problem if there is one.

I would also make sure all of your plug wires on the coils two clicks, not one. Also make sure they are on your plugs tight. If still no problem found, pull all your plugs out and examine the porcelin. Look for any cracks or hairline black lines. Sometimes a plug may look good, but it may be cracked where you cant see.

As said above, check for maybe wire arcing to ground. Park somewhere dark and open the hood. Look for any arcing to grounds from the plug wires. If you dont see any, grab a spray bottle with water in it and spray the plug wires. This will usually show the problem if there is one.

I would also make sure all of your plug wires on the coils two clicks, not one. Also make sure they are on your plugs tight. If still no problem found, pull all your plugs out and examine the porcelin. Look for any cracks or hairline black lines. Sometimes a plug may look good, but it may be cracked where you cant see.

This is almost exactly what I was going to say. Sounds like a misfire to me. Check everything the way joshp14 said.

I dont understand. Why do you say coolant temp sensor wire? How would that cause problems.

The coolant temp sensor causes the car to surge and buck. Basically it acts like you are saying. The car will seem like it's running on 4 cylinders It plugs in at the front of the header on the drivers side beside the number 1 plug. A few people have damaged the sensor or messed up the wire doing headers.

I do think it's a burnt wire somewhere. AS long as you ignition system is fine (wires, plugs, and coils). You need to get up under and check all the wiring. A burnt o2 wire will cause this as well. If it gets real bad it will start popping fuses. The transmission lockout, engine control fuse, maf, and 02's are all on the same circuit. So if it gets burnt up good or is actually resting on the header it will eventually start popping the engine control fuse.

I just wanted to add that the car will still run with a blown engine control fuse. It will act like you are saying. Under the hood by the drivers side, check the fuses. If it is blown, it's almost guaranteed a burnt o2 wire. If it is blown and you replace it, then it blows again after running the car or driving, you know its a burnt wire.

Was there a fix to this guys problem yet. As i have the same friggin thing going on in my car. Iv checked for arcing and dont see any. Tomorrow im changing wires to see if i have a bad wire, if not then ill check the plugs and then move on to the wires on the temp sensor and O2 sensors. Im even going to change out the O2 sensors to see if its a problem. I report back with my solution hopefully. BUt im having the same exact problem.

Problem was solved this morning pulled plug for the number 1 and found it to be cracked in 2 spots. I also found a plug with a messed up tip where the wire snaps on so i replaced it as well and no problems.