93cruiser

History.
The car died while traveling 55mph. The car would not restart and it had a slight misfire ocasionally. Since the opti had been wetted down on two separate occasions and the ECM did not throw any codes except for code 12 I thought the opti had died again. I took this oportunity to replace the opti with a MSD unit with vacuum venting. I put it all together less coolant and hoses. I tried to start the car and it exhibits the same no start condition with a slight missfire.

I have spark
I checked the fuel pressure-42 psi
ECT is connected- no codes
I have not tested the injector coils- need a test light

Any help would be greatly appreciated.
93cruiser

93cruiser

Okay,
I have gotten a little farther along. Now I am getting a consistant backfire through the intake/TB. The MSD opti is keyed so that it is timed when installed, right? The GM unit is keyed so it can not be installed out of time. I assumed the MSD unit would be the same. Please let me know. Thanks,
93cruiser

jfb

During cranking, use your timing light to check timing.

93cruiser

I am not aware of many timing marks on the damper or a tab showing the degrees. I am working on a LT1 with the optispark. I am going to recheck my plug wires though. This time I will have help so that I have them properly traced.
Thanks for the reply.
93cruiser

schrade

No start with a misfire is kinda' confusing there '93...

Do you mean no start with almost fire? Or a start with a mis-fire?

Redeasysport

On a 92/93 it is possible to put it on with the key out of position. Take the spline out of the old one and find that "sweet spot" were it slides in&out very easily an align the new one to that angle. When you put the new one on it should slide in easily and "pop" against the timing cover with hardly any effort. If you had to pull it in by bolting it it is definately out of position.This happened when my ex mechanic did my first one. Then I had to argue with him about it after he opened up my sealed and upgraded 95 cover( add insult to injury he stripped the cap bolt putting it back on).

If you find that the install was correct the ICM is the next place to look but I bet it is in wrong.

93cruiser

Sorry about that. What I mean is I am getting blow back through the intake consistantly on one of the cylinders. I have not noticed any flame to this blow back, but it sounds like I am getting some ignition. Other than that noise, the engine turns over with no hint of combustion.

I have rechecked the wires and they are correct.

It is behaving exactly like it did when the engine failed on the highway before the new msd opti was installed.

I will ohm out the injectors and check to see if their getting current as the engine turns over tonight.

Any other suggestions would be greatly appreciated.
93 cruiser

93cruiser

I have replaced opti's before. The opti is a delicate device and bolts should never be used to pull it up to the timing cover. The opti install is not the problem. Thanks for your input though.
93 cruiser

93cruiser

If I disconnect the ECT sensor wire should the ECM throw a code? I did this and I did not read any codes other than 12.
93cruiser

schrade

I think you will get no codes for anything disconnected until the engine warms up and it goes into closed loop mode (checkin' measurements from all sensors).

PurtyLilC4

the car dying while going 55mph would have lead me to check the altenator and ignition coil as a couple of the first things, but with what seems to be one cylinder not firing correctly it sounds like the opti. Have you checked the coil? a bad ground on the coil or just a bad coil would kill your car as well.

93cruiser

I am getting spark so I have not checked the coil. I will check the ground strap to the ecm. The ground bundle on the transmisson bell housing is good as well. I will verfy that the njectors are recieving the firing voltage tonight.
Thanks for your reply.
93cruiser

schrade

Instantly? Or slowly / boggin' down / shutdown like?

Redeasysport

If you're sure the opti is right it has to be either the wireing or ICM. Double and triple check the wiring. My car did the same thing when the opti was off a few degrees. Backfires out of the intake can only be 2 things wires or timing.

Oh and lets not forget the MSD optis, according to Gordon Killebrew, are junk. They do have failures right out of the box reguardless of how many people rave about them.

93cruiser

I have not adjusted the timing screw. Is it possible that it is off enough not to run? Having this adjustment on a LT1 seems rediculous. I guess you need a scan tool check the timing. I thought the ecm adjusted for slight varaitions of timing on the optispark or a worn timing chain. BTW the injectors ohm out at 13 ohms. I performed the noid light check and all of the lights were blinking brightly.
According to the FSM I could have a open EGR. Has anyone had a similair experience?
Thanl.
93cruiser

93cruiser

Guys, I still need help. In addition to the facts above I have done the following:
1) Verified that the MSD rotor matches up with the factory opti rotor position.
2) Spark plug wires are correct.
3) The injector coils ohm out at 13 ohms.
4) The Noid light test shows all injectors are getting a pulse.

Question: would a vacuum leak from the EGR cause a no start condition?

Thanks for any help.
93cruiser

schrade

No. By itself, a leaky EGR port will not create a no-start.

Randy93

You might want to check the opti again, if it just died and would not restart. You might have a bad opti or a bad harness, do a search on 93jetkockey, he had the same problem. Turned out he had a bad harness, he did a big right up on his problem.

Redeasysport

Wasn't that that the Tach Filter problem he had?

I agree with the recheck opti. MSD's are not all perfect. Might be time to return it.

93cruiser

I finally have the time to work on my sick 93 vette. I have confirmed that I am getting a consistant spark. All of the above is still correct. I took the ICM off and had it tested. It was bad so I have ordered a new one. With the ICM bad is it possible to still get a spark out the coil to the plugs?

Any knowlege here would be helpful. I hate the idea of throwing parts at this think.
93 cruiser