After I installed the Dynatech headers I have had some problems concerning the check engine light constantly coming on. Well the codes keep on saying missfire on the number 5, 2 and 7 cylinders and really there not missfiring at all. I dont know if the headers are doing it or I am just having problems with the engine, but it runs great. Ill turn off the codes then a day or 2 later Ill be driving and all the sudden it comes on???

 

Come on guys!!!

 

I have heard with the random missfire code that the CPS (crankshaft position sensor) might be off and have to be realigned so to speak. I think you can only do it with a Tech 2 at the dealer though. Have you removed your PCM lately?

The other thing is I had random misfire codes recently (right after I had done my exhaust/header work) go figure, and it turned out that I had forgot to plug one of the o2 sensors back in. Check all the connectors. I had removed the pass front conn. by the frame rail to make removing the old sensor easier. It must have been late at night and I figured I would connect it the next day. Then I forgot so I bet that is it. Truck ran 100 times better with that connector in place.

00z71sierra

 

I have never removed the PCM but I am gonna check the sensors out.

 

Well since my buddy is out of town picking up parts for his vette I was unable to take it to his shop to diagnosis the problem. So I took it to autozone for the check, and once again the number 2 cylinder is the problem. The truck isnt misfireing at all, but its happened a couple of times and you can tell when its missfireing. So before work when I pulled into the parking lot there was no snow and the ground was dry so I got under the truck to see if any sensors were loose, none. But I looked at the clamp above were the crossmember is at and it was way loose and there was black exhaust gas all over the pipe. So im thinking the exhasut leak is what is giving me the random missfire codes. What do you guys think?

 

I have never heard of an exaust leak throwing a misfire code . But i think 00z71sierra maybe right about the CPS. You might want to have that checked out.

 

yes a exhaust leak can and will throw codes such as missfires and 02 lean codes.

 

Check the front o2 sensors to see if they are tight, A week after my Dynatechs were on the drivers side front o2 came loose. They are a bitch to get tight the way they are in the cats unless you have a o2 sensor socket. Does it pop or sound like it has a exhaust leak? Mine would pop when I got on it real hard.

 

Replace #2 spark plug.

 

move the #2 plug and wire to a different cylinder. see if it moves.