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Random stumble/misfire... grrr... UPDATE 3-19-08


spiderw31
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Yes, I do have an update...

 

After running short of ideas, I got the CKPS changed and the car is running MUCH better, but still not right. Throttle response is greatly smoothed out, and the stumble / shudder is much less severe, but still there to some degree. Using my timing light, I'm still seeing random no spark events, but now only on cylinders 3 & 5, and very occasionally on cylinder 1.

 

The shuddering seems to be the worst at very light throttle, so I tried swapping a new TPS in, and that made no improvement. I've swapped my Autolite wires for AC Delco, and while it didn't change how the car runs, they sure do fit better :high5:

 

Seeing that the problems are most obvious on the cylinders with long plug wire runs, I'm beginning to think I might have weak spark. Would Rapidfire plugs be an improvement in that scenario? Also, what is the resistance of the coil pack supposed to be?

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:willynilly:

:evil:

:gr_mad:

 

OK I've officially had it! The just up and died on me again today, EXACTLY the way it did a couple weeks ago. Just driving along, and it quit with no warning. No it just cranks and no start.

 

I'm gonna get it to run, and then I'm getting rid of it. I'm done.

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:willynilly:

:evil:

:gr_mad:

 

OK I've officially had it! The just up and died on me again today, EXACTLY the way it did a couple weeks ago. Just driving along, and it quit with no warning. No it just cranks and no start.

 

I'm gonna get it to run, and then I'm getting rid of it. I'm done.

 

Let it set a couple of hours, then try starting it again.. When I had my ignition problem, the car would die when it would get hot and just crank, not start. I let it set a couple hours, and she'd start right back up again...

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I doubt it since I didn't have the problem before changing the ICM, and it seems odd that two would die at the exact same time. Probably should check them though...

ive seen 2 coils gone bad at the same time before. not uncommon, specially where they are located.

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I doubt it since I didn't have the problem before changing the ICM, and it seems odd that two would die at the exact same time. Probably should check them though...

 

 

Question for you.. Did you use the dialectic (sp?) grease that came with the igniton module?

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Wish I would have read this thread earlier.. You have a LQ1, right.

 

1 of 2 things have happened, timing belt stretched and/or finally broke, OR, the ECM file was corrupted or the ECM had an issue and finally died

 

Or, you just have a wiring issue now that I think of it.

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:willynilly:

 

Two words.

 

Timing Belt :sad:

 

Just went back out to try to start it up (thinking along the same lines that time might just do the trick) and no dice. So I pulled the inspection cover to, and the belt is frayed and shredded down to about 1/3 the original width. Watched the belt while my wife cranked the ignition, and there was no movement of the belt.

 

I've got AAA coming to tow it, and I'll snag a couple pics of it when they come by.

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Dam dude, that sucks. Will be interesting to see if it solves the stumbling/misfire. Forgot to mention I changed my 3100 timing chain and cogs as a precaution around 195k, didn't make a difference. I've got a 91 Z34 too and felt like I spend more time fixing the POS than driving it. One word for you...GOODYEAR. Don't mess with the DAYTON/DAYCO crud, had one bust within 15-20k of changing, no signs of wear, next one about the same mileage, stripped the teeth on the belt. Never any oil leaking on the belt, tension was right on where the manual said, new rollers every time. The GOODYEAR Gatorback outlasted the others by leaps and bounds, was the last time I changed it. I only use GY Gatorback serpentines now as well, last way longer than anything else I've tried. Do it yourself if you would rather pocket around $700 or more. Will probably cost around 200-250 for everything. Since that car I refuse to buy anything with a timing belt.

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I dunno if this really had anything to do with the stumbling since that seemd to be spark related, but we'll see. Anyways, here is what I found when I looked at the belt:

 

beltfail.jpg

 

What gets me is I inspected the belt on Saturday, and it looked exactly the same as it did when I inspected it two months ago when my ICM took a dump. So somehow this all went bad in the last 80 miles :rolleyes:

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Jesus christ.....thats probably the worst one ive ever seen. My jetta was almost as bad. The tensioner seized and made my belt look almost as bad as that. Luckily it made a horrible sound and I caught it just in time. I gave it another 5 more miles before it snapped. Your lucky that ur wonderful LQ1 isnt interference. How many miles are on that?

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Your lucky that ur wonderful LQ1 isnt interference. How many miles are on that?

 

You're not gonna believe it, but 43,500 miles. I'd say the real factor here is that it is 16 years old.

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OK, I'm at a loss here...

 

Swapped coils in, and it made no difference, so I exchanged the ICM. The new one behaves EXACTLY the same, with the stumble at cruise RPMs. :willynilly: I've double checked my plugs and they look great and are gapped correctly. I swapped in a known good MAP I had laying around just for kicks, and no change (didn't really expect anything though).

 

The ONLY other thing I can think of right now are the plug wires I just put on when I initially changed the ICM, but they don't appear to be bad (no light show, everything is solid), or that I really should just spring for the AC Delco ICM and be done with it.

 

Any thoughts?

I belive i had a post about the exact same thing when I joined and it was indeed a plug wire on the rear of the engine, It was cut, check the wires.

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I dunno if this really had anything to do with the stumbling since that seemd to be spark related, but we'll see. Anyways, here is what I found when I looked at the belt:

 

beltfail.jpg

 

What gets me is I inspected the belt on Saturday, and it looked exactly the same as it did when I inspected it two months ago when my ICM took a dump. So somehow this all went bad in the last 80 miles :rolleyes:

JESUS FUCK! I never saw that pic beofre but I wouldnt even drive that anywhere.....change it asap.

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:willynilly:

 

 

I've got AAA coming to tow it, and I'll snag a couple pics of it when they come by.

 

 

Hey Chad, what part of that sentence didnt you understand ??

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If the belt went that quick, I bet one of the idlers or tensioner went out.

Thats what happend to my z34 . and come to think of it about 2 weeks

before it went it devloped a stumble just before it would shift into 2nd gear. and after changing the belt it has not had any stumble at all.

Your belt just could have dry rotted from age cuz thats not many miles and probaly never been changed.

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Any update? Been having a similar problem periodically w/ my 95 GP 3100, 206k and still doesn't burn oil, had it since new. Feels like the engine fires on 3 cyl for a few secs or will drop in RPM for a sec like fuel was cut off, doesn't matter which gear, seems to be more apparent in 4th OD since the TQ is engaged so when it jerks its that much more noticeable. Replaced plugs/wires followed by TPS, both crank sensors, all coil packs and the ICM, checked and double checked the wiring harnesses but no change. Strange thing is that it only seems to happen around 70 degrees and above which means it is happening quite a bit now being I am in FL. I also have a throttle delay occasionally which led me to the TPS but the replacement didn't make a difference. Did all the other typical servicing including EGR passage, injector cleaning, throttle body, etc. Had a bud years ago with a 93 GP and his EGR would carbon up after 10-15k and would cause all kinds of stalling/hesitation issues. Haven't had a chance to test fuel pressure, pump has never been replaced. Anyone else out there with any ideas? Could it be the PCM overheating or just going bad? Can happen within 1-2 min of driving. Anyone know how much dealers charge to flash a PCM? Had a ton of wierd stuff happen w/ my 88 Corsica, PCM would overheat and the engine would die till it sat turned off for a few min. Ironically the PCM was the cheapest thing to replace on that car.

 

This is an awesome site, been here for a while but first posting.

 

we had a 95 grand prix with the 3100.. it eventually died on us after 3 fuel injectors quit. It had the same symptoms as your's and yeah, you may want to have that checked out or you'll find yourself eventually stranded. You could try some fuel system cleaner (get the good stuff, not the cheapest) to clean out injector deposits and also change your fuel filter to reduce the load on the fuel pump. I'm almost positive that its either your fuel pump or injectors so be careful.

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Don't feel bad, thats what they end up looking like most of the time. When I said the first one busted it ended up looking like yours. A cord breaks and the rest of the belt can't handle the tension and within a few miles its dead. Just remeber to get a Goodyear Gatorback. If you want to have some comparo fun, ask for a Dayco one too, you can feel how rubbery the Dayco is vs the hardness of the GY. The factory belt on mine busted around 24k, dealer replaced under warranty with a Dayco belt. Then I replaced it twice on my own with a Dayco belt as it was the only brand I could get w/in a week. Got smart and held out for the GY for the third time on my own. Now it seems most AutoZones have the GY in stock or can get it within a day. Never any situations with any rollers going bad or weak tension, it just happens. This is the part of this engine that sucks A??. Compared to myself and a few of my buds that had these engines, you got lucky to have that may miles on it. Make sure you don't have any oil leaks or pwr steering pump leaks, my guess is no based upon the cleanliness of the fray in the photo. Biggest killer is the amount of heat these engines build up and the amount of tension needed to turn the four cams. At least GM did one thing right in making it a non interference engine.

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