270Mike

I have a 1996 Z28. No internal motor mods. Free stuff and SLP shorty headers (leaky gaskets). Here's my problem:

While driving down the road I noticed a lack of power. I'd floor it and it would sputter (while halfway pulling) and be a general pig. It seemed that if I turned the key off, then back on, it would not do it for a few moments.

I parked the car, then decided to run it again. It sputtered hard and I kept on the gas. It seemed to clean itself out for awhile, but a few days later it came back very badly. It seems to happen when the outside air temperature is high, but that's not conclusive, yet.

I autotaped it and got a bunch of codes:

o2 sensor (various) - I have simms that dragged on the ground, so they are shot. It's been this way for years, now. No trouble.
0300 engine misfire detected
030x cylinder x misfire detected - It will be a different one -usually 1, 3, 5, 7- after every reset (clear codes).
0171? fuel lean bank 1

I watched the misfire count and I am getting heavy misfires on all cylinders, but numbers 7, 5, 3, 1 (in that order) are the highest by far. Misfire counts in the thousands (history).

I went to check the coil, but i'm not sure which wires are which.... The Chilton's manual isn't the greatest.

I replaced driver's side (bank 1/1,3,5,7?) plugs and greased the plug boots on the opti and the plugs. That didn't help, although I needed to do it. I'm running NGK TR5s.

Can I check the opti without having to remove it? I was getting good spark before this all, even on nitrous runs.

Any help is appreciated.

Mike Williams
1996 Z28
1992 TSi AWD - no A/C :-(

EDIT - Also, I forgot to add this: The car reeks of gasoline when I am idling and have the vents on. Only when it's misfiring, though.

270Mike

one TTT post for hopeful assistance. i'm stuck, guys.

aintno6

For one you should replace your o2 sensors and get rid of those exhaust leaks. When I had my exhaust leak the car lost noticeable performance in that alone. And that wasnt even that big of a leak. Also I noticed that because of the leak at times the pcm was retarding the timing because I guess it was translating the exhaust leak as false knock.

How old are your front o2 sensors? I noticed yours is a 96. So even if you have O2 simms. Your front o2's may need to be changed out, and are giving up flase readings. Which may be some of the problem.

But as far as the missfire goes. It sounds like it is opti related. Does it missfire only under WOT? How many miles are on your opti? Your probably not going to tell if the opti is bad, unless you remove it. And if you are removing it, you mind as well replace it.

valter

Driver side front O2, I think. Probably exhaust leak made it run rich on that side and damaged oxygen sensor. How it's running in open loop?

kevm14

According to the FSM, running rich won't permanently ruin an O2 sensor, only temporarily desensitize it. A lot of exhaust volume with high EGTs will generally clean up a temporarily fouled sensor (just mash on it?). Of course, this is after you fix your richness problem.