Remember my problem from last fall? First it was the EGR, then the Dynaspark?

Well... it did it again today... I was driving home and the engine started to buck on me. No backfiring - AND NO CODE! -, just this strange thing that acted kinda like this:

run for a few seconds - miss from hell - run for a few seconds - miss from hell - run for a few seconds - miss from hell.

Then it smoothed out.

New Racetronix fuel pump, tons of other new things... New EGR valve...

I am going to bring my laptop tomorrow, and run a data log. See what is happening when it blows...

Ever think bout buying a mustang as 2nd car ?

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I wonder if it's mechanical at this point...valve sticking open, etc?

I'm watching this thread closely.....

I have a subtle 'stumble' for a few seconds(like 1 cylinder not firing)every time my AC engages. It's more than 'normal' or simply 'drag'...it's quite unusual and obvious. I'm thinking perhaps some glitch in the PCM.

Anyway, I'm hoping you find your problem Bogus.

I have had this problem off and on for several years... It finally went away for "good" once I got the new EGR and the Dynaspark service... so which was it?

The problem existed before the Dynaspark existed, too.... so this has been around.

I used to think it was bad plug wires, and I have remade them several times... nah... no changes.

My setup, to remind folks, is the dynaspark, with LTCC. This has 8 coils and takes high voltage away from the distributor.

The LTCC is fine, it was given a clean bill back in Jan.

It started to creep up a couple of weeks back... it would do it once and then be fine. Usually when cruising...

It was a hard miss, to... BAM! BAM! but no codes...

It could be mechanical, but why would it just stop like that? It did this for about 1 mile.

As I said, data logging this bitch.

Oh, 183k miles... LT1, MN6... 1992.

An update... it did it again yesterday, on my way home from a Corvette show I was judging.

The interesting thing... it didn't do it GOING... only coming back. And like work on Friday, it only did it coming, not going. It's like something is heat soaking. It gets warm in the morning, the sun heats it more during the day as the ambient temps rise, then I drive it home and it gets hotter and then it fails. This sounds electronic/electrical.

Again, no codes.

I am real tempted to go buy a cheap Gen 1 opti and swap it out... just to test my theory. I can't believe it will be any worse than the Dynaspark.

My thinking is this: If the problem goes away, then I have nailed the problem. What do I do next? I donno... Bob @ Dynaspark has provided good customer service and has been nice to deal with, however, when I ask technical questions, I get no answers... so I am of the mindset that he simply replaces the electronic pickup and sends it back. He has no testing rig to diagnose the failure.

This is getting me thinking of upgrading the entire thing and doing an LSx controller and harness, but if I do that, why not go LSx, too?

I started this thread last fall to brainstorm ideas... to solve some of the more nasty problems...

http://www.corvetteguruforum.com/modu ... id=159108#forumpost159108

If you want me to send you a different memcal for testing, let me know.

Axel - Thanks for the offer. I hope the memcal isn't the problem.

It stalled at a light today. Also stumbled a bit but it was stop and go traffic and I think I disrupted the rhythm of the failure! I think a code was thrown, I need to test for that.

Another shocking twist... nothing happened yesterday. Ran like a champ.

I really hate this type of problem... I really do...

a couple of hic-ups... nothing to write home about. as long as I keep the laptop in the car, threatening to do a scan, it behaves.

well... 2 more days, no more problems. about running great.

Like I always say; (or somebody else once said)

You can't fix what ain't broke.

Maybe you had more bad gas. Are you still using the same gas station?

I use Shell... but as I said in another thread, the damned gas gauge is - after 8 years - actually working. Figure that one out.

I wonder if a bunch of crap / sediment was breaking off or stirring up and going into the fuel system? Might be time to change the filter again.

I might do that... burned off some water? Possible.

Now the bitch won't start... Cranks but no start...

I may have pissed off VATS. More tonite...

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Andy, do you have the starter relay bypassed?
A VATS problem won't let the starter spin.

Then either the ECM is dead or the opti is...

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Do you have a spare ECM?
If you don't, I do.

I do! Thanks!

it started... go figure...

A little more detail... I did check fuses and codes... both were clear.

I checked a number of connectors underhood, and they appeared to be fine. I did find one connector, it powers the coils, that might have some gick on them. I am going to remove that connector and hard solder it tonite.

This is getting annoying...

driving home tonight - and it did it last night, too - it starts this little pulsating stumble thing.

It's like a miss, but not like a miss... I can't believe at steady cruising that a single cylinder would make it do this, it's like a momentary shut off, then on. And when I momentary, it's a blip. half second? tops? Besides, if it was a single cylinder miss, I would expect it all the time.

I am going to hook up the ol'laptop to it tomorrow and see what I learn. I think it's become consistent enough to diagnose.

Ready to put an optispark on it yet?

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Interesting, that's what my GM opti did before it got worse, not even enough to throw a code.

I'm not real familiar with the setup your running I have seen the dyna spark before, though I thought the setup I saw had 4 coils with 2 towers each on them.

If it's an ignition issue, it almost sounds like the optical sensor in the distributor is failing with the crank/no start... otherwise I was thinking the igntion module could be failing but again I'm not familar with the exact setup you have since if your running....

Rememeber the ECM is taking it's RPM signal from the optical pickup on this.

If it cranks an does not start I'd want to know that I have the fuel injectors being pulsed or not. Assuming we have the fuel pump turning on which I doubt is an issue right now but a possibility for a no start of course.

If they are not being pulsed, then I know I'm probably not having the ignition coils being fired either.

A Labscope is very helpful in checking these types of things. you could see what the actual singal patern looks like vs a voltage reading on a meter or if a test light is turning on or off..

-=Rick

I am leaning to the dyna failing again.

I will be hooking the laptop up tomorrow and doing a data log.

My setup is the LTCC, which is like the DelTeq, except that uses lost spark, mine uses 8 LSx coils.

This is the result... in both csv and ALD file formats format. I noticed a bit,that things dropping off... fuel to zero and timing down to three. it also fits when, in the drive time.

Attach file:

---

July152012.adl Size: 369.86 KB; Hits: 134
July152012.csv Size: 997.58 KB; Hits: 122

Whomever looks at the datalog... now, I reference the CSV file, vs the adl, but this should still work.

ok... looking at sample 817 and 818, these seem to be endemic to all the other ones that act about the same.

TPS goes to zero.

Spark to 3* advanced.

knock retard = zero.

left and right bank = zero.

EGR and carbon canister = zero.

the next time this happens is at sample 930.

it's like everything just shuts down for a moment. Fuel is dead, timing is sucked back...

Sample 1057 shows the TPS at .78%, which means my foot is still somewhat on the throttle, yet the rest of the numbers are above.

Sample 1243 to 1247, I was in 6th gear, hence the low RPM ratings. But the effect is nearby the same.

If you look right above the 817 section around 790+, you are also losing TPS percentage there, BLM drops, IAC drops, carbon canister % is zero. I wonder if you have something internal in the ECM that has an intermittent connection? Like a quad driver or whatever they call those chips. I'm no electrical component guy. Is there one spot from the ECM that controls all of those?

Or could a bad TPS/wiring cause all of that?

Then look at sample #826. Like there was a spike that screwed up everything, then back to normal a second later.

This almost seems like an electrical/computer problem?

Matthew

I am beginning to suspect the TPS myself. If it is sending bad data, that could throw all bets off.

As for the ECU, this happens regardless which ECU I use, but a good thought. Also, the system throws codes real quick for quad driver failures.

Anyone know how long a "sample" is? how many samples make up 1 second?

The fuel/air average (BLM) is looking real lean. GM is shooting for 128 +/-10, above is lean and below rich.
The ECM is fighting this suspected lean condition with some real high injector pulse width milliseconds. With injector M/S that high, it could be almost a rich stumble caused by an overreaction.

BLM is maxing out at 160 on top and 108 at the bottom. Your BLM values are real close to max all the time.

The IAC is sometimes all the way closed, but not all that bad to suspect a real bad false air issue.
What injectors do you got? The yellow Bosch from FIC?

I think those are the injectors, yes. I will confirm. I did get them from FIC about 3 years ago.

My injectors are ORANGE.

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Wasn't there a thread (or opinion) on the FIC injectors for 92-93 only that they had a small problem in idle or midrange and that recently FIC had made a change?

I could be wrong but that's been in the back of my mind.

You are correct. Jon and I spoke about that... but I think mine are post fix. I need to talk to him, I will ask.

Ok... the miss/drop out really got me this morning... I tried to merge and at 3/4 throttle is just died for a fraction of a second! BAM! Then on the next shift, same thing. I don't know the RPMs for sure, but I am guessing about 4k.

No data logs.

So... Opti? TPS? Gremlins? Pacers? Javelins?

Andy, you've fixed/checked/replaced everything on that except that stupid aftermarket dynaspark. That's where I'm leaning.

And if the optical pickup or whatever it is called is going bad, that could explain why it loses spark temporarily then picks it back up at 4000 rpms, right?

I tend to agree. I have a new fuel pump, filter, coils, plugs, wires... what's left?

There are no codes... the LTCC specs out ok...

Given the intermittent issue, you may want to check your harness.

I have... and will again... but I don't beleive that is the culpret.

You still have the LT1 for your wife's car?

If so, since it won't cost anything, why don't you swap out parts and see what makes the problem go away?

1996 <> 1992. I can't just swap parts. Thought about that but it ain't happening. That's why I plan on swapping engines.

However, new twist. I didn't see these codes appear at all when doing the data log, but I am going to review the data tonight... the twist... I got loss of COMM - C41 - on the CCM and H83 - loss of spark data - from the ABS computer.

That sounds fishy... like the entire ignition system is shutting down if only for a moment.

I need to confirm that the grounds are good and clean.

Yesterday at lunch, it got real ignorant... start, stop, won't start, wait, start, stall... did this for about 10 minutes... then ran fine the rest of the day. Odd, eh?

That's when I found those codes from above.

I went to the #1 possible cause...the point were the EST data is sent - the famous 2 white wires that feed the tach and the ECM with RPM data, and the pink wire that powers the coils.

In that circuit, I had a sketch connector doing it... so now, it's all gone and there is only one solder joint, with heat shrink, vs several and a suspect connector.

I also found one of the 4 fuel rail bolts was REALLY loose... like .5" back threaded! Figure that one out.

Today will tell me if any of those fixes helped.

Oh, I can't just buy another opti... I will have to swap guts, because I don't have a detachable cable on the Dynaspark, and my old cable was a cobbled up POS anyway. My plan is to buy a cheap shit Cardone reman, move that sensor over to the DynaSpark and see what happens. I will then return the Cardone, with bad sensor, as CORE... not just return it, that was be like wrong and stuff.

you might want to try taping a fuel pressure gauge to your windshield for a couple of days and see what it reads. i found i had a heat soak problem when i did this .just a thought

New Racetronix fuel pump, and I do have a FPG on the rail. So far, no signs of pressure loss.

this morning, it ran like a champ. Just maybe?

man problems like this can really boggle the mind .