Well, I posted the other day that I drove my car to work and is was missing at WOT. Seemed like an ignition issue. Then I drove it yesterday to Rick's and it was running like crap again. OK at idle/low throttle, but stumbling, hesitating, and missing when you'd give it hard throttle.

I pretty much narrowed it down in my mind to a few culprits:

Ignition system (because of symptoms)
Timing (thought dist might have slipped)
ECM (since I had a comm error before when datalogging)
Loose chip (I have zif adapter)
MAF (intermittent code 33 over early spring when I was driving it in cold weather)

The other day I checked the plug wires and they seemed fine.
Last night I checked the timing and it seemed fine.

Swapped the ECM this morning, made sure the chip was set in tightly. Took it out for a drive and at first it seemed to run well for a few blocks. Then it stopped running well and the symptoms were:

Weak acceleration/general slugishness
Flat spot in acceleration 3400-4000 rpm
Backfiring when downshifting to accelerate around 2200 rpm

I came home and swapped the MAF with a used one I have in the garage (borrowed from Woodstock - thanks Axel!). Took the car back out and it was totally different. The weak acceleration is gone, no more backfiring, ran totally different. It's still not where I think it should be, but I'm wondering if the tune is out of whack since I changed the MAF. There are documented problems with changing MAF sensors especially on modified cars. I'm gonna get another MAF soon so I can take Axel's out. Then I need to do some more datalogging. I need Mick to change a few parameters.

But as for now, the MAF seems to have been the culprit. I don't normally throw parts at a problem, but since I already had them it only took a few minutes to swap out. I'm gonna have to check my plugs, too, I think they might be fouled up from it running wrong for a bit.

Just thought I'd share in case anyone else runs across a similar issue.

Matthew

Aren't those also the issues mimiced by they optispark? I know you found the issue, but I'm asking for my own knowledge in learning about these cars...

And on that note, you just toss around processes like "changing my plugs" like its an everyday thing. That experience still gives me chills, especially that one on the back side by the air box!

Ralf

It's nice to have spare parts lying around sometimes.

Glad you got it narrowed down.

Ralf - it's funny what we think is normal/easy/everyday. PeteK rebuilds transmissions in his sleep and I think they are the evil monster under the bed

As far as your question, the optispark is misunderstood by a lot of people. It's a distributor. People give it some golden pedestal status because it has a different name. So I would say that any ignition related problems can be "assumed" to be related to the optispark, just as much as a normal distributor.

Jeff - it is handy to have extra parts around. I don't toss anything if it's still good. I save every single part I take off in the thought that one day, someone might need it, even if it's not me. You should see the boxes of random crap I have saved. Some of the parts I accumulate when I see a good deal in the f/s section or on ebay, knowing I might need it some day. Axel (who I borrowed the MAF from) is even more meticulous and finds ebay deals like a sniper. I know because they get shipped to my house before they get sent off to Germany. He's a bloodhound sniffing out parts deals.

Matthew

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Ralf, he has an L98, not an LT1.

Well, duh...lightbulb going on moment. But, I've never changed the plugs on an L98, so it might still be something I'd sweat over whereas Mattew would do it in his sleep.

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Great, finally you got a chance to check it for me. Glad it works, but somehow I got the strange feeling, it won't make it out of the States

I trade it for some of your random crap

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Sign here:

My experience when guys swap MAF sensors is that is has an efect on the tune. In some cases the changes aren't too bad when swapping with an original OEM one, but any "rebuild" or aftermarket has been dramatic.
You can send me some data and I'll make the needed changes and whatever else you have in mind...no problem

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Just changed my plugs (and wires, cap & rotor) last weekend.
Really not to bad of a job. The drivers side is easy, the only one that's a challenge is cylinder #2 behind the A/C compressor. Remove the acces panel in the fender well and by using a swivel and a combination of extensions on the 3/8 ratchet and it wasn't to bad.

But you're correct, Matt probably could sleep through it....lol!

I don't care what tools you use #8 is still a pain in the butt. Unless you've deleted the HVAC system.

Matthew, Mick is dead on.. When my MAF sensor went bad halfway through my tuning all the rebuilt ones I tried were way off of spec..I couldn't for the life of me find one that was even close to the factory MAF sensor..That's why I went to the Blowerworks MAF sensor, now if I ever lose a maf sensor all I have to replace is the Ford maf sensor blade for about $75.00 instead of the whole Chevy unit for $700.00. My Corvette now has a MAF sensor with a 2005-2010 Ford Mustang sensor blade and I couldn't be happier...WW

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If you mean that it froze up during recording, that is a known problem with the 7165 ECMs. Some seem to be better than others. Only thing that helps here, engine off for a minute or two. It's not a laptop, interface or program issue, just the ECM unfortunately.

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Nothing to worry about. When it runs well, that's burned up in no time.

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Jeff-
I didn't think 8 was as tough as 2, but they are a challange on the passenger side!

You guys give me too much credit.

Anyway, the car was running hot after I changed the ECM (before MAF) - it got up to 237* on the highway in 96* heat. It never runs that hot...ever. It was running hot the day before, too. Looks like the problem was a shredded serpentine belt. That's a speculation at this point, but seems legit. Don't know how/why but it was frayed bad and huge chunks missing out of it. I still need to determine the root cause.

I noticed the underhood light wiring was hanging down and damaged as well as a couple of the plastic push clips that hold it in. I don't know if the plastic push clip came loose and damaged the belt (you could see where the plastic was worn from rubbing the belt/pulley...bad) or if the belt frayed/came loose and the whipping action hit the wires and caused the damage. Either way, I have to repair the wiring and I already replaced the belt. I might have to do what Joe did and run the wires internally...his install looks great.

Matthew

Checked the plugs and they are not fouled in the least bit. Electrode is in perfect shape as is the strap. Porcelain is still white with a little grey blob under the electrode. Not brown. I am thinking it's either just right or running a little hot. Could be from the car running hot the day. Not sure. I'll keep an eye on things.

Matthew

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Matt, those pics are plugs ther have been run....forever.

You won't see anything like that on your motor.
Maybe you could post a good pic of a plug and someone like Will can give you a read.

Just a quick note say "THANK YOU"!!!!!! to Matthew for spending an entire night off helping a newbie (to Vette's anyway!) change out injectors.
Matt is a true enthusiast and a great guy. I'm in debt to ya Man!!
Thanks again Matt.

No problem, Mike, I had a great time. We'll get together another time and do some more projects!

Matthew

Well, it seems I found the reason my belt was fraying. I inspected the air pump and found the pulley wasn't lining up. I took it off and flipped it around and there it was...perfect. I didn't even know the pulley had "two sides" but it does. So make sure if you ever take it off it goes back in correctly.

As a second note, my main fan wasn't turning on I found out. Seems to be my warm running temp issue. Comes on with the aldl so it seems to be a relay or something else, not the fan motor.

Matthew

Matt, I guess the MAF I gave you didnt work. Sorry It worked when I took the old motor out. When I put the new motor in I just replaced everything. Hopefully the other parts will be of use

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Honestly I didn't get a chance to swap it in. I used one from Axel before I had a chance to stop by your house and that solved the problem. But I still appreciate you holding on to it for me. I'll have it as a back up or for testing when needed

No worries, It's just that I would have felt bad if you drove all the way to my house and the part didn't work.