86 Turbo Z misfiring, running poorly

[Lee'sdaytona]

Greetings,
My good ol' 86 Turbo Z, (project car) Stock TI, 5spd, mopar Performance LM, maybe 2,000 miles on the wires/plugs/cap/rotor.
It has been running great for months now. I drive it sporatically, say at most once a week, at least once a month.
Today, I went to drive it after a two week sitting period. I started it and it was idling poorly and running very rich.
I took it around the block and returned home. But when I pulled in, it ran fine. So, I figured maybe because it had not run for awhile, something needed to wake up (stupid thought) So I set out to meet some friends. Of course, about twenty minutes into the drive (running nicely) it started to stumble again. I limped it to the local school where my brother teaches and left it.

My buddy said he thinks the timing belt jumped a tooth. Sure its possible, but to run like crap, run great, then like crap again? Then I was thinking maybe the old original mopar coil is weak/going out, but he doesn't think so. Could be maybe a computer problem? I also have trouble with it stalling at stop lights. The SDS is one with low miles that I bought new at the dealer like 7 years ago. Could a failing map sensor or problem in the logic module do this? The smoke from the tailpipe was black it was so rich.
Thanks for any tips. I plan to go at it tomorrow.
-Lee

[BIGBRUDDA]

Howz the weather been in Jersey lately? WET? Run it around ,n dry it out.

[Lee'sdaytona]

Well, yes, we torrential downpours for a week straight. I drove it right after that, and it ran great. Then we had a week of extreme heat wave, which it sat through, followed by some more rain. I suppose its possibly with leaky t-tops there is water getting into the LM. What should I do if I go start it tomorrow and its running normally again!?
-Lee

[trannybuster]

Carry a fuel pressure gage and hook it up once it starts it acting up....

[turbovanman²]

Any codes?

I would guess the oxygen sensor is sticking, next time it does that, unplug the sensor and see what happens, if she smooth's out, replace it.

[Lee'sdaytona]

Well, no "Power Limited" lamp, though I know that doesn't mean there are no codes stored. Thanks for the tip guys!
-Lee

- - - Updated - - -

[Lee'sdaytona]

Ok, I limped it home today. Codes 21, 26 and 45 (what is 45?) showed. At some point, the PO installed a 4-wire O2 sensor, and what I found was at the harness plug, it was poorly rigged with electrical tape, and spade connectors sliding onto the pins of the o2 harness. Two wires were not attached at all, just hanging. one to ground, one to the original underhood wiring harness. I know the 86 should have a single wire o2. So, do I need to replace the o2, or is there a correct way to install? The wire colors were Black, White, Red and Yellow, and I have no idea which one should connect to which.
All that said, somehow the car ran beautifully the way this 02 has been set up for awhile?
-Lee

[iangoround]

Are there two white wires? Those are usually the O2 heater circuit. One side should be grounded and the other should go to a switched 12v source. The black wire should be the O2 signal, and the other wire should be the O2 signal ground.

The correct way to install a 4 wire O2 sensor is to get the matching harness-side plug and wire it up. Failing that I would just replace it with a single wire O2 and call it done. They warm up plenty fast enough. Alternatively, if you're running a wideband with a narrowband output like the LC1, feed your LM the narrowband output from that and call it a day.

[Lee'sdaytona]

There are not 2 white wires. There are Black, White, Yellow and Red. I just assume order a single wire o2.

I was reading about this 86 600: http://www.turbo-mopar.com/forums/sh...single+wire+o2

It sounds much like my problem? but I am going to swap the HEP first. Thats a simple thing to try. I'll order a new o2 single wire, because after all, my goal with this is to restore it to original stock condition, even if that means using inferior original to 1986 parts. Any suggestion on brands to get and to stay away from? Rock Auto has them from $8 to $36, the most expensive being the AC Delco one.

- - - Updated - - -

HEP swapped, and although it seemed to run a tad better, definately did not solve the problem. Still blowing black smoke and idling rough. next Im going to order a proper single wire o2 and try swapping logic modules. Also, the wiring harness is in very poor shape. Many of the wires going to the Power module plugs are cracked exposing the conductors, and the harness has been pretty hacked over the years, so I'll swap in one i have from an Automatic 86 Turbo Z

[iangoround]

Even with an unhooked O2 sensor, it should still run pretty ok and not usually rich and crappy. Have you checked all of your vacuum lines? I had an 85 Laser that ran like crap because there was a leak in the vac line to the MAP sensor. It ran pig rich and very rough until I figured it out.

If you're swapping engine harnesses with one from an automatic, remember to ground the neutral safety switch wire to the transmission case. Also while you have it out it can't hurt to pop each of the pins out of the LM connectors and bend them back to make better contact with the LM. I just pulled the harness out of my turbo z for a major overhaul/rewrap and bending the LM pins helped a lot.

[Lee'sdaytona]

Cool! Thanks for the additional tips. It will give me more avenues to check out. I was thinking maybe map related as well. I will def. check the vac lines, though it is idling around 900 where it should. Perhaps if gas got into the line via a bad FPR? I'll keep at it!
-Lee

[Lee'sdaytona]

I swapped in a different MAP today and it ran great. Does this mean my problem is fixed? who knows? But I'll keep driving it around and if it becomes a problem again, I will be back for more!
-Lee