I was driving 2 days ago when the engine started to have a slight miss to it. I put it in neutral and reved it a few times and cleared it out. There was a bit of black smoke that came out when i did it but nothing too major. Then I was driving it that night, and it started missing again, only this time it was a bit worse. More black smoke etc...Now it is running pig rich all the time, it surges, idles erratically, and really surges and misses bad especially when the car is fully warmed up. I unplugged the MAF and drove it. It seemed to be a bit better at first but then got just as bad as when plugged in. I checked for anything obvious and couldn't find anything. The SES light did come on but I haven't had it scanned yet. Being that it runs badly when cold or hot rules out O2's right? Could my opti be going bad? I did check my fuel pressure and it's at 42 lbs engine running. I sprayed electrical contact cleaner on the MAF and it didn't help. The intake elbow is tight and on right. It's weird - the car was running perfectly and then all of a sudden the slight miss. Now it's really bad. It's almost like something slowly died or is dying. Help!

 

I'm having a similar problem, but my car is a 93, and has a new motor.

Please let me know if you figure out what’s going on.

 

Both of you need to look for a dead cylinder. I responded to DJ about the PASS system DTC also. Oh and BTW, anytime you run pig rich, you should check the oil for fuel contamination. Just smell the dipstick.

 

Ok, the car runs fine until it gets to about 140 degrees. Then it starts to miss. As it gets warmer, the miss gets worse. It starts running really rich. Thick black smoke comes out the exhaust.

 

Okay that not exactly what mine is doing. My car just continues to get hot, and I'm really starting to think that that problem is being caused be a faulty/clogged Radiator.

The stumbling, well I'm not to sure what’s causing it be here’s what I'm going to do.

1. Replace fuel filter - needs to be done anyways, and wouldn't it be nice if that fixed it

2. Readjust the valves.

3. Leak down test / Compression check. - Although their new I've heard lifters can cause really bad stumbling, if their spongy, and it's really apparent after the car gets hot.

4. Replace Coil

5. Replace ICM

6. Replace Opti - god I really don't want to do that, although I guess I've been lucky; the car has 130K miles on it I've never changed it.

7. At this point if I still haven't fixed it, I'll scratch my head, pick my ***, and go have a beer and try to forget about the whole thing.

Can you guys think of anything else?

 

Well I switched the MAF with a known good one and no change. Also changed the MAP and no change. I changed the plugs just for grins and no change there. It's looking more like the opti. I changed the coil with a known good one - no change. The code I get is for random misfire. Opti is coming off. Update later.

 

could be 02's. I could visible see my engine shake when the right bank went out. 20 miles after my header install. Light would come on and off. Try looking for a massive airleak somewhere. I had an exhaust leak at the header. My tailpipes where caked thick and black as hell . Tightened that up and tightened the y pipe up and have not had any problems since. In fact it was feeling sluggish when it was rich but it ran so much better after the leaks were tightened up.I suppose the o2's were reading the extra 02 and dumped fuel to compensate

 

could be 02's. I could visible see my engine shake when the right bank went out. 20 miles after my header install. Light would come on and off. Try looking for a massive airleak somewhere. I had an exhaust leak at the header. My tailpipes where caked thick and black as hell . Tightened that up and tightened the y pipe up and have not had any problems since. In fact it was feeling sluggish when it was rich but it ran so much better after the leaks were tightened up.I suppose the o2's were reading the extra 02 and dumped fuel to compensate

 

Yep,
Right O2 sensor was bad. I changed the opti, plugs, wires, injectors, MAF, cleaned throttle body, and changed the computer. Still ran like crap. Switched out the right O2 first and bingo! It was running PIG ASSED RICH! The 30# injectors probably didn't help that.