Znewb

Hello all,

As the title states I've got a 96 Z that's running super rich, to the point that the exhaust smells only of pure fuel and it visibly blows fuel vapor. I'm an auto tech but I specialize in 4 bangers and this "Real" engine has me stumped.

Before I list the DTC's I'll give a brief history to help better understand.
The Z has sat for the past 5 years in my fathers backyard untouched due to an issue with the optispark (Go figure.) Because he couldn't afford to fix it at the time it was put on the back burner and all but forgotten.

Long story short the Z was given to me for a reasonable four quarters to which I towed it to my shop and went to work. After removing the water pump to replace the optispark and discovering a broken wire in the optispark pigtail and repairing, I regained spark.

Gave the Z a good once around, new fuel system (pump, filter, injectors, regulator), plugs and wires and while at it deleted the air pump and plugged the bungs.

As it stands I've got four DTCs stored in the ECU and what feels like a dead skip in addition to the nauseating fuel vapors. P0100, P0300, P0412 and P115.

Any insight?

Injuneer

P0100 indicates a static MAF sensor reading. This is often due to lack of 12V power to the MAF sensor. With key on, measure the voltage between the pink wire (12V from fuse panel) and black white wire (ground) in the harness connector. Should be 12V. If it isn't you've found the problem. If it is, next suspect is a faulty MAF sensor. If your multimeter has a frequency scale, measure the frequency between the yellow wire (frequency signal to PCM) and the black/white wire. At idle you should see about 2,600Hz. Or try unplugging the MAF sensor so the PCM defaults to speed-density mode.

P0300 indicates random misfire. If you have access to a scanner with GM Enhanced Parameters, it should be able to access the misfire count by individual cylinder, which will sometimes point you to the problem.

P0115 is not listed in the GM code list specifically for your vehicle:

http://service.gm.com/gmspo/mode6/pd...c57P_FY_yE.pdf

P0412 is telling you the electrical circuit to the AIR pump is faulty. Either the fuse is blown, the relay is faulty, or the *****AIR pump has been deleted*****.

Znewb

Thanks for the response Injuneer,

I unplugged the MAF to rule it out during the initial Diag and realized that it didn't change the way the engine ran, but I didn't probe the connecter which is the next thing I'll do.

I've, since posting this have corrected the misfire. Apparently I wasn't attentive to the routing of my wires and had one laying on the exhaust manifold (Duh.) but even still it's blowing unburned fuel from the exhaust.

p1153 was the code, I apparently had a typo moment with that one.

Anyhow, After correcting the misfire she's running a lot better but still, as stated above, is blowing fuel vapor from the exhaust. I'll test the MAF circuit and see if there are any issues there and post my findings.

Thanks!

Znewb

Apparently I had forgotten about this thread so i'll update it.

As stated in other posts, it turns out that my #8 injector was defective and stuck open, causing tons of unburnt fuel to enter the exhaust. The issue was resolved kind of old school.. I pulled each plug individually and found the one that was drenched in fuel.

Hope this helps someone in the future!

mrmint69

What brand were the injectors?