Hawg55

Put the hardtop back on the car for winter storage, and thought I'd run it for a bit. While it was sitting there idling the RPMs' started to fluctuate and then it would stall. It would start back up and run and then do the same thing again after a bit. Any idea what the possible cause is????
Codes keep changing after I clear them from h16 one time to h36 the next. Could it be the cap and rotor or is it the optispark itself?

1993C4LT1

Did you see black smoke from the exhaust?

Hawg55

no it is not running rich

Hawg55

OKs o the car started this morning and than dies again. Checked for codes and here is what I got: Module 1: H74...Module 4: H16 H33 H36 and H42...Module 9: H62....Any ideas????

94z07fx3

Rat eating/peeing on/nesting on your harness?

pcolt94

What year car? There is nothing in your profile either it find out.

Codes are all over the map and would not run with anything yet. But I would check for spark and fuel pressure. If you lose your low resolution pulse (error 16), that will kill the engine.

I am more inclined to look at the ICM first which is a huge cause of loss of spark and interment conditions.

After it stalls, does it start up again? If it does not, that's a good time to check for spark.

Hawg55

It's a 93. Three weeks ago it quit running and would not start. I started getting parts together, new optispark, water pump, plugs and wires, optispark harness etc in order to replace them. I went out the other day to check something on the car and it fired right up and ran great for a couple of days. Now it's dead in the water again and wont start. It will run at times for a few seconds and then not start.

95BLKVette

Bad ICM won't throw a code 16!

But a bad Opti will.....speaking from recent experience

Hawg55

Went out this morning to clear codes and the module 1 code h74 and module 9 h62 codes were no longer there so I cleared all the module 4 codes. The car started and ran for about five seconds and died. Checked for codes after cranking a bit to see if it would start and there are no codes and it won't start.

lt4obsesses

Fuel pressure?
Fuel pressure regulator?
Spark at plugs?
Spark at opti coil wire connection?
Spark from coil?

Previous indicators or sudden failure?

Keep in mind that codes with an 'h' are history codes and not active codes.

pcolt94

With posts 6 & 10.

You have checked the codes as a beginning step which is good. It went nowhere so now forget about them. You're not going to fix it looking at codes.

It's going to require actual troubleshooting of fuel and ignition system. Since it is an intermittent problem, the actual defective part (which we don’t know yet) may not check or test bad. Once you determine the problem area and then narrow it down to a possible part, replacement may be the only way to definitely ascertain the problem. I'm not saying to throw parts at it but to troubleshoot the problem as best as far as possible then make the best possible decision.

dizwiz24

I really hope you didnt cheap out and buy a non new old stock, non OE optispark.....

Any optispark other than OE (ac delco for 92-94) or delphi from 95-96, are junk.

Even the expensive $500 MSD optispark is junk as it doesnt use an OE grade mitsubishi optical sensor.

If that optical sensor inside the doesnt have the mitsubishi symbol on it, then your car is on borrowed time... Or in my case, i couldnt even get it out of the garage after a new optispark install (the brand was ac delco 'remanufactured').

Note that the AC Delco 'remanufactured' optisparks recycle the optical sensor that was on the base core. They do a great job replacing seals, bearings, but unfortunately 'reuse' whatever optical sensor was on the base core.

Hawg55

I got a NOS ac delco optispark part number 10457702 and an msd cap and rotor so it will be vented. It has fuel, it has spark have checked all of that. Haven't installed any of the new parts yet as I am trying to figure out what is causing the problem. Dont want to just throw parts on it and not repair the problem. If anyone else has experienced the same problem please chime in. I am leaning towards the optispark being bad, or the cap and rotor being bad. When the PO bought the car he had the cap and rotor replaced along with the water pump about 7k miles ago, but they were replaced with NAPA parts at the cost of $1000.00....

Den14

Check for gas smell on the oil dipstick or the vacuum hose that goes to the manifold from the FPR? Had a similar situation with my 92 LT-1. I had the black smoke of open injectors dumping fuel into cylinders. I got injectors from FIC and they are so much better than the MUltecs. You should not smell gas in the oil I found out!

lt4obsesses

What was the fuel pressure?
How long did it hold after turning the key off?
FPR in good shape?

So it has spark?
Good spark, weak spark?
At all the plugs, the opti connection, the coil?

Hawg55

Today is my late day at work, so I figured I would do some more investigating on my problem. So I go out to the car and it starts right up and runs great???? Once it stops running it will not start at all but it seems if it sits for a few days it will fire back up and run.....I am waiting for the service manuals I ordered to arrive so I can diagnoise the problem more, but has this happened to anyone on here, and what did you find as the problem???

lt4obsesses

Few more questions.

When it started up, it runs as normal? No misfires, stumbling, rough idle?
How long did you run it? Just briefly, or brought up to operating temp?
Have you checked for gas in the oil?

Might want to try taking the ICM to a parts store and have it tested. It's real easy to take out. But then again, you said it has spark, I assume you tested at the plugs during the no start condition. If that's the case, then you can pretty much rule out the ignition being the problem.

Still curious about fuel pressure. I wonder if the pump has a weak connection, or condition that creates a shut down or overheat that shuts it off? Or if your fuel pressure regulator is malfunctioning?

The MAF and the MAP sensor are the other things that come to mind as well.

tombrammer

I had a very similar problem with my 93 some time ago. It was the ICM (ignition control module) connector. It was lose inside, the prongs were not making a good connection so the car would start and run but when it got fully warmed up the heat would make the prongs bend and lose contact. It would not restart for hours, only after the motor cooled down completely. I found it by jiggling wires while the motor was running, when I jiggled the wire and connector to the ICM the engine would stumble and almost die. I pulled the connector apart and bent the prongs a little to make good contact. It's worth a try. Good luck.

airplane50

This is the best advise you can get. dizwiz24 said it best and knows what he's talking about. Would add, check your water pump. If its leaking change it. Also change your antifreeze and add the GM pellets to prevent future leaks.

dizwiz24

If waterpump is leaking then change it...

If the waterpump is not leaking then do not change it...why?

Because the waterpumps you buy today are ac delco made in china. Not as good as oem.

Adding a tube to the weephole is a great idea to divert water away from the optispark.

I also rtv silicone seal the optispark as added insurance in case the seals crack.

Though to be honest....ever since i put in 160 tstat and reprogrammed the fans, the coolant temp never goes above 180f.

Optispark seals look great vs. The oem units seals when the car ran at 210 to 220f. The oem optispark seals were all cracked allowing wsater intrusion and causing that units destruction!