missing/rough running round 2
 

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.

Re: missing/rough running round 2
 

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.

Re: missing/rough running round 2
 

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?

Re: missing/rough running round 2
 

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.

Re: missing/rough running round 2
 

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.

Re: missing/rough running round 2
 

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.

Re: missing/rough running round 2
 

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

Re: missing/rough running round 2
 

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

Re: missing/rough running round 2
 

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?

Re: missing/rough running round 2
 

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.

Re: missing/rough running round 2
 

Further testing, I put the meter on D7 off the ECM and with no key in the ignition, OL. With key in but off, OL. With ignition turned ON, I get a cycling resistance to OL, repeating over and over. No idea what that means. :)

I also figured out which key code I have, and for $26 from Ecklers I can order the VATS bypass which is nice and clean, no soldering required. I wouldn't miss it at all. But the question is, would that fix the problem? For 26 bucks I'm inclined to order it anyway.

Re: missing/rough running round 2
 

I don't like to make guesses in trying to diagnose a problem long distance, BUT, we had similar symptoms or a ZR-1 here is WAZOO recently. It turned out to be a failed ECM. Do you have access to another ECM? I would not recommend buying a replacement until the issue is fully ID'd, but if you can borrow an ECM and run it for a period of time, it may help isolate the issue.

Any year ECM will work, just put the chip from your car into the "test" ECM.

If you don't have access to an ECM locally, PM or email me (jim@gizmosart.com).

Jim

Re: missing/rough running round 2
 

If the car starts, it is NOT a VATS issue.

Jim

Re: missing/rough running round 2
 

There have been times when it has cranked but not started. Then next time it starts, runs and then stops cold. Then times when it runs like total crap. According to the WSM, with a broken VATS circuit it will still crank. At this point it could be a flaky connection/ground in that circuit or like you said, possibly a bad ECM. Still not certain exactly, but I REALLY appreciate the offer! I need to do a little more digging.

Re: missing/rough running round 2
 

I did order the VATS bypass from Ecklers, although 10 bucks for shipping a small light part is ridiculous. But I like that option better than breaking out the soldering iron. Meanwhile I'm cleaning grounds and checking all the connectors. I hate electrical issues.

Re: missing/rough running round 2
 

Shipping and Handling has always been a big profit center for mail order sellers...Bob

Re: missing/rough running round 2
 

Last night I planned to order the similar Mid American part (with the toggle switch - I thought it would be nice to leave VATS working most of the time, and deactivate when troubleshooting), but after adding $17 shipping it was close to $80. They lost that sale.

Re: missing/rough running round 2
 

sounds like a bad ground, ecm, or wiring problem with the spark module

I had a 93 that would do this if is wasn't driven enough

the dis module would code, it would run rough or cut out and then start back up and run fine

definitely get a scanner on it and start wiggling wires!

Re: missing/rough running round 2
 

When my injectors gave up the ghost it was similar to the OP's situation. Ran fine all day at a school, last run it broke down a bit at high rpm. Cooled off and was fine on the way home. Next event (one week later) it was fine in the morning runs, phew, but then came the afternoon - idled reasonably maybe just a touch "off" but when I hit it it was 7 cylinders for sure.

At this point with the e10 gas I'd look pretty hard at any OE injector. Measure 'em and it may well tell the tale.

Good luck,
- Jeff

Re: missing/rough running round 2
 

I installed the VATS bypass from Ecklers this morning, and it's perfect. Drove the car a good long time, got everything nice and warm, not one problem, not one hiccup, running absolutely perfect. I swear it's running smoother than it did before. I tried multiple stops and restarts, cruising, full acceleration, gentle pull from a stop, and it's back the way it's supposed to be. Apparently my VATS was flipping out, causing erratic running issues.

Very happy with the $27 fix, not so happy with the $10 shipping. But for all in less than 40 bucks not too bad.

Re: missing/rough running round 2
 

Not so much. It's been 4 weeks since I wrote that, 4 weeks since I even opened this forum, 4 weeks of grumpy.

Not the forum's fault, been annoyed with my car. After I wrote that, I took the car out again and it drove fine. Enough I thought it was cured and headed out to dinner with the wife. Nope, didn't even get out of the neighborhood before it was coughing and wheezing, barely running. I felt lucky to get back to the house. I was so thoroughly irritated I just ignored the car for an entire week, driving the 308...until I noticed coolant on the ground under it, but that's another story.

After a week I had calmed down and decided to figure out once and for all, just what the hell was going on. I pulled out the WSM, test light, volt meter, and started tracing everything. Every single thing checked out, grounds excellent, wiring good, but still bad running and codes that just didn't make sense.

Finally in desperation I called up Russ McBride, what a godsend to have a fellow Z owner so close by. And a great guy too. He offered to let me try his ECM in my car, to eliminate that as a possible issue. So I headed out, and on the 1.5 mile drive to his house, it coughed and chugged the whole way. 10 minutes later I was driving a completely different car. Russ' ECM totally transformed it, beautifully smooth and powerful. The difference was stark, and a little shocking. No doubt about it, my ECM had serious issues. At least it was a relief to finally know what the problem was.

Next call was to Marc Haibeck, what a great guy. I've bought a few things from him, but definitely one of his smallest customers. Still he spent the time on the phone with me, helping me understand the issue. With his help, I was able to ship my ECM off to hopefully be repaired - in his words, it works about 75% of the time. I sure didn't want to try and source one if I could help it, so it was worth rolling the dice.

Got the ECM back a few days ago and holy hell, it ran just like with Russ' ECM. Smoother than I remembered...so much so I think it must have been gradually going bad, and I didn't notice until it got really bad. I haven't posted until now because I wanted to keep driving, just to be sure it's truly fixed. I've had the car out daily for the past several days and it's running like a champ, not a hint of problems any more. Even took the wife to dinner, to make up for that bad drive 4 weeks ago. I'm knocking on wood, crossing fingers, and other superstitious stuff....but I believe the gremlin has been banished.

I had actually considered selling it at one point, but not any more. Great driving car, love it. Again.

Re: missing/rough running round 2
 

GREAT! ECM issues are the most difficult to resolve. When they are working properly, the ECM self analysis of Sensor input is invaluable. Not so much when the brain itself is sick.

Enjoy the Summer!!

Re: missing/rough running round 2
 

Glad you got it fixed.... On post 6 I offered up my scanner would have been a big help to you.

Re: missing/rough running round 2
 

Very true, but then I wouldn't have had the last 4 weeks of entertainment! Actually when the Z went down, the 308 became my driver and then it went down too, with a coolant leak. That left me totally without a car, dependent on an unhappy wife for transportation. Let's just say the less I asked of her the better. :)

Really appreciate the offer though, but just no way I could get down there. Hell I barely made it around the corner to Russ's place!

Re: missing/rough running round 2
 

Diamonds and kissing *** will get you back in good sted with the Wife.....