Boozer350

I have a 99 Z28 M6. I recently put headers on it and deleted the rear o2's and EGR. I got it up and running and it ran ok but the wide band was showing full lean at a heavy throttle. I took it to a friend with hptuner to tune out the o2's and egr and to see if we could get the leaning out problem cured. So he pulled the stock program off of it and saved it and loaded in a tune he got from hptuners and the car started to run bad. Then started turning on the ses light and it said number three cylinder misfire. So we put the factory tune back in it and just took the o2's and egr off to keep the light from coming on due to them not being there and it started to run worse and the third cylinder misfire code still continued to come up. We tried a different coil pack but did cure it. I'm dying to just drive the car but I've heard everything from spark plug to ecu could be the problem. If anybody has had this problem I would love to hear your fix. I'm dying to just drive the car and have spent way too much money to get to where I'm at and still feel like I'm a long way from figuring it out.

1320

iTrader: (6)

Sounds like the the problem is two fold. When you have a miss, you get raw fuel in the exhaust, which it will try to correct.....by leaning out the whole bank........

The miss sounds real...but doesnt have to be 3....it might be 3 or a close cylinder. I would guess burned wire first since you did headers, then plug....

Shut the light off, start it and see if the spark is jumping to the header....

Get a laser heat gun, and verify the dead cylinder by temp checking the header tube about 3 inches from the port and look for the low temp....They idle in the 550-700 area, a dead hole will ussually be 250-400 degrees
, depends on the tune some, but one will be noticablly colder than the others

Boozer350

Thanks for the info. I'll give that a try.

Boozer350

Ok so I checked fire on all the cylinders with a coil pack light and checked all my plugs and wires. Still no luck and running horrible! Anybody else have any thoughts before I just put a carburetor on it! Lol

1320

iTrader: (6)

just by putting headers on, it would run just fine. Lean, yes....but still run just fine. You wouldnt delete the o2 s to richen it up....you would change the ve and pe table possibly. Seems like your tuner, may be the issue, not the car.

Theres about 100 ways to ad some fuel in the tune, and so far you havnt lead me to believe that was done.