missing/rough running round 2

[8cam]

Replacing the coils, wires and plugs cured my last issue but it's happened again only different. It's still my daily driver and has been running flawlessly since I did the coil fix. But I had two issues occur in the last couple days.

Wednesday I drove it to work just fine. When I got in the car to go home, I started it and idled for a minute, and it just stopped. No chugging, just quit, first time this has ever happened. Started right back up and drove home fine.

Then Thursday I drove to work again, just fine. Time to go home and first start didn't catch, and I thought I had just let it go too soon. Second start and it was definitely running rough. I drove it a couple miles and dropped off a colleague, then headed home, still not running right. The difference this time is it still pulled all the way to redline, just like only 7 cylinders were firing.

About halfway home it started running REALLY badly, had to work the throttle just to keep it sorta running, like half the cylinders were gone, or an old carburetor in need of a rebuild. I pulled off the road and checked under the hood, nothing looked out of place, hose on the MAP sensor right where it should be. Started it back up and it ran PERFECTLY. WTF? I mean it was on it's last breath just a few minutes ago.

So I continued driving home and it ran just like it should, pulled hard to redline, just perfect. Right before I pulled in the driveway it started the slight stumble again. This morning I had to move it to get my other car out. Started up and ran perfect again. Again WTF?

I'll start pulling plugs today, also need to check fuel pressure. I'm guessing fuel problem, maybe the filter is clogged.

[RussMcB]

Ugh. I hate these kinds of problems.

My thoughts for problems like this are, how can you prepare for troubleshooting for the next time it happens, to help you identify the problem?

For instance, it would be nice to have a fuel pressure gauge already hooked up and readable from within the car. That's something I've thought about adding, but haven't looked into it yet.

I can't think of any great ideas for pre-adding some type of test lights to let you know if something isn't getting the voltage it needs. (I'm thinking about doing that for an occasional no-start issue I'm having).

If you can think of any easily swapped out parts that might help you troubleshoot, I'm nearby with my '91.

Good luck.

[Halinmontana]

Would there be enough interest to hold a work day in Atlanta if there are enough cars located there similar to what WAZOO in Maryland and FBI does in Illinois? I would be willing to come up from Panama City Beach or offer to hold it down here with warm weather guaranteed for the event to help out with each other's issues?

[RussMcB]

Originally Posted by Halinmontana

Would there be enough interest to hold a work day in Atlanta if there are enough cars located there similar to what WAZOO in Maryland and FBI does in Illinois? I would be willing to come up from Panama City Beach or offer to hold it down here with warm weather guaranteed for the event to help out with each other's issues?

That's a generous offer. I'm pretty sure I would attend, and probably benefit since I'm just getting familiar with these cars. Thank you.

8cam - Sorry for the thread tangent. Hope someone jumps in with some good suggestions for you.

[XfireZ51]

8cam,

An intermittent like that sounds more electrical than mechanical. I would pull the connectors on the ECM and re-seat them. Check any connectors you can reach like MAP, TPS, Ignition Mod etc.

[We Gone]

I agree it does sound like an electrical issue maybe just a lose connector. Let me know if I can help. Not sure if it will help but I have a scanner.

[XfireZ51]

Originally Posted by We Gone

I agree it does sound like an electrical issue maybe just a lose connector. Let me know if I can help. Not sure if it will help but I have a scanner.

Absolutely throw the scanner on it. See if there are any dropouts on the sensors.

[Paul Workman]

Originally Posted by XfireZ51

Absolutely throw the scanner on it. See if there are any dropouts on the sensors.

I couldn't agree more! Being able to data-log during normal and during the "event", is priceless! (Best tool I ever bought!).

[Starman]

I saw where you went after the ignition, but did not see where you checked the Fuel Injectors. But they are not typically intermittent. I would check all grounding straps, especially the big ones from the engine to frame. A lift is best for this if you have access to one. Might also want to check fuel pressure, could be bad pump?

[8cam]

Well I pulled the codes and at first got a 42 but I believe that was a false code, because it can be tripped when engine rpm drops below 400, which it certainly did. I have not seen that code since. However I've pulled code 46 three times in a row now, with the car driving beautifully and then suddenly stopping. Confirmed by getting code 54 from the CCM.

Damn VATS.

An intermittent VATS connection certainly explains the bizarre behavior I'm getting. So now my options are to "check for open or short to ground on CKT 229" (which my dubious electrical skills are suspect) or disable the system entirely.