keepers15

I have replaced my opti spark and motor will not run. It does fire but sound like something is keeping it for running normal,I ran the codes and am not getting any codes. spark plug wire are correct. It will not rev up when I step on ther gas,idles at 400 rpms any ideas will be helpful also its a 1994 lt1

tblt44

could be a bad opti but I really don't know.
What brand Opti did you put in and are you sure the opti ws bad brfore you replaced it? What was the symtoms before the replacement?

93cruiser

Did you have the ICM tested. The failure mode of the ICM can be like it is out of time or the plug wires are not correct. Oreilly Auto Parts will check the ICM for free. Cannot tell you how many times I thought the opiti was bad and it turned out to be the ICM. BTW, the ICM is located just above the coil.
93cruiser

keepers15

I replaced the opti because I had a miss at ldle and sometimes while driving

keepers15

ignition control module

surfer93

Did you diagnose????????????
Or throw money at the problem and close your eyes and pray?

surfer93

Is the car backfiring or just missing badly?

You might not have put the coil and spark plug wires on all the way.

keepers15

plug wires are correct I removed the new opti spark and installed the old unit, same problem. I replaced the opti because of a miss thinking it was the opti. I will run but only at 400rpms i push the gas and it will not rev sounds like it staving for gas. it ran fine until I replaced the opti ALL this started after replacement of the opti

93cruiser

Typical ICM symtom. It is easy to remove and have it tested. Icm's can fail quickly and often. I am not not to keen on the chinese built ICM's.
93cruiser

keepers15

Had ICM check at Oreilly's and test ok what next

JAKE

Then the question becomes 'Was the Opti correctly installed?'

Several guys have installed them wrong in spite of the claims of some that it can't be done.

Ask ShoeBox 'bout that; he's on LS1LT1.COM

Jake

keepers15

I could understand this if I had not tried two opti sparks, when I installed the first one car would not run, I check plug wires to make sure the were correct, replace plugs thinking they were fouled but no. Had ICM checked at auto parts and it checked ok.

93cruiser

I hate to say this but here it goes. Have someone else check your plug wire arrangment. It is hard to be sure about the drivers side since it is so tight. Having said this two misplaced plug wires will not cause the problem that you are having.

Try unplugging the battery as well. This will reset your computer.
Next, check the strength of your spark. The coil could be weak.
I failed to mention the obvious which would be bad plug wires. Check for arcing in the dark.
93cruiser

JAKE

The guys who mis-installed them said pretty much the same thing. How SURE they were they installed them correctly. But hey it's your call.

Jake

92WhiteVetteGuy

Hi,
Verify spark plug wiring using the numbering on the old cap as a reference (save for future use). It is very easy to get a couple cylinders crossed.
Did you inspect the inside of the Opti?
Any Corrosion, oil and antifreeze damage?
Check the cap for carbon tracking?
Did you remove/replace the old spark plugs/wires? What was the spark plug gap compared to the factory spec?
Did you install/route a vacuum harness? If not you will not get long life out of your new distributor and could be replacing shortly down the road!
I went through replacing the Opti on my 92 C4 LT1 back in 2006 due to carbon tracking from worn out spark plugs. The gap was approximately 2X factory spec.
I am now replacing my WP failing after 75,000 miles.
Inspection of the Opti showed no damage.
I have replaced my plugs twice and will be replacing again.
SPARK PLUGS DON’T LAST 100,000+ MILES!!!
Should be good for another 75,000.
Let me know what you find?
Best of Luck,
92WhiteVetteguy

keepers15

(1994 lt1)Here is what happened, car would idle very rough with the tach jumping. After it warmed up I would get a miss at high speed. I replace the opti spark put everything back together and started the motor. Would not run and idled at 400 rpms. I inturn thought I had gotten a bad opti and installed my old one to see, samething 400rpms and will not rev. I did check plug wire routing and it is correct, had ICM checked and it's good,replaced plugs. Ohmed the injectors and they showed 12.6/12.7, checked for loose wiring, everything check ok. It seems to be out of timing, checked codes and am not getting any codes

timmy 93

Take a look at Fuel pressure and your fuel pump.

Showcase1186

Sounds like you are having the opti blues. First and foremost check your firing order, then after that, check it again, then check it one more time. It really sounds like a firing order issue to me. If that does not help, then be sure to inspect the harness that plugs in to the opti. They terminals in the harness tend to corrodejust as much as the opti itself. Use a hook and pick set to "gently" bend the contacts on the pigtail to ensure a proper connection to the opti. This solved all my opti blues... Summit also sells a replacement harness for the opti if your is really bad.

Gregs 93 Vette

Hey has anyone mentioned to check your spark plug wires??? (Ok, I'm joking...) I'll be the first to say I'm sure you know what you're doing and can look BEYOND the plug wires! It does sound like it's starving for spark though... No sparky, no revvy... I'd start looking at the root of the spark and see where you're losing it (coil, etc).

JAKE

What we could be seeing here is a mind-set problem.

If one goes into a diagnostic procedure believing that all is well, correct, installed right, etc., chances of finding the cause of the problem is much reduced.

However, if one goes into a diagnostic procedure being SUSPICIOUS of everything; SUSPICIOUS that it's NOT correct, NOT installed right, etc., then finding the cause becomes much easier.

I checked "this" and it's fine and I had "that" checked and it's fine isn't getting us anywhere since the problem persists. So, obviously it's something that's being MIS-DIAGNOSED or MISSED ENTIRELY. Otherwise the problem will be fixed by now.


This is not a personal attack; it happens a lot on this and other Forums. Guys believing and posting that everything they checked was fine - yet after many, many post exchanges they finally discover and admit what they "thought" was correct, in fact wasn't.

Best advice is to attack this thinking that EVERYTHING is WRONG or at the very least SUSPECT. Have diagrams in front of you and pay meticulous attention to even the smallest detail. Many guys can't or won't do that.

A second pair of fresh eyes often pays off too. Eyes of someone who isn't pre-conditioned to believing everything is RIGHT/CORRECT. He can be more critical and objective.

Following the Trouble-Shooting procedures shown in the Factory Service Manual for your year car is a good starting point. That'll eliminate a LOT of guessing and assuming. That's exactly why I always invest in FSMs for my cars right after I buy them so that, when the day comes (and it surely will) I'm faced with a similar situation I can approach the fix in an intelligent, systematic manner.

My thinking now is this isn't going to get fixed unless and until there's a change in how the diagnostic procedure is conducted.

It's all about being suspicious of EVERYTHING and Attention to Detail.

Jake