My Father in law that lives with me has a 1994 Z28 with the LT1.

After significant body work We had the car painted.

When it came back from paint, within a few days the Fuel pressure Regulator Failed and dumped fuel directly into the intake.

Fixed that, at a local shop.

Within a Week, injectors on the Divers side all became contaminated. Flushed the fuel lines, replaced the fuel filter and the regulator again, and installed all new 24 lbs injectors. Fuel pressure 32 at idle and 43 ish under acceleration. (My son and I did this work)

She ran GREAT for about 2 months.

All of a sudden she started Just randomly stalling out and could not be restarted for 20 min. NO fuel pressure. Just replaced the fuel pump with a Delco pump, fuel control relay and ANOTHER fuel filter. Pressures are perfect again.

4 days later, stumbling under acceleration, which has now progressed into erratic idle and not drivable.

Using Scan9495 (which had no codes before with the other issues), Now I am getting the following codes:
DTC 16 -- Distributor Ignition System (Low Resolution Pulse)
DTC 36 – Distributor Ignition System (Faulty High Resolution Pulse or Extra Low Resolution Pulse Detected)
DTC 41 – Ignition Control (IC) Circuit (Open Circuit Detected)
DTC 42 -- Ignition Control (IC) Circuit (Shorted or Grounded Circuit)

Since I had a known good Ignition Module and Coil, I threw them in, and the codes come back and no improvement.

I know this is most likely the Opti unit (which is a delco unit that was installed about 6 years ago) Another indicator is that it seems worse as the humidity goes up....

My question is, why does this thing seem to be having cascading failures, Just bad luck or should I be looking closely at something?

 

Was it allowed to sit unstarted for an extended period of time with old, E10 fuel? That would explain the fuel problems. Also depends on how many miles…. it’s a 27+ year old vehicle. Fuel pressure regulator failures are fairly rare. Plugged fuel filter is rare, unless using poor quality, or contaminated fuel. Pumps generally fail from running the tank too low. Simultaneous failure of 4 injectors is pointing to poor fuel quality or contaminated fuel.

Opti is an endemic problem. Some troubleshooting is required:

4th Gen LT1 F-body Tech Articles

Current problem, with sensitivity to humidity could be as simple as corrosion of the harness connector that plugs into the Opti. The 93/94 Opti's, lacking the later vent system, are prone to corrosion from ozone buildup. Check the harness connector for a greenish corrosion buildup, damaged pins, or damaged wire insulation. Can also be the result of not replacing the Opti timing cover seal when replacing the unit.

 

Note, it was in the shop for paint (and taken apart) for a few months. My theory, The failure of the regulator started all the fuel issues. My father in law had it towed to a cheap shop and I dont think they properly cleaned the fuel rail. I pulled slivers of thin plastic out of the fuel rail when I flushed it replacing the injectors. I am thinking that the shop didnt get all of the old diaphragm out of the system. The fuel pump could have been a coincidence but I can help but think that bypassing all that fuel and running at full blast when the regulator went bad didn't hurt it. I replaced the fuel filter both times for good measure, they are cheap.

The ignition issues are what are confusing. Unless it is just from being in the paint yard so long.

 

The fuel pressure regulator is on the outlet/return side of the rails. Not sure how anything from the regulator could get into the rails.

 

Me either. Its all very confusing,

 

OP

If your current Opti is a true original AC Delco than keep it. You may simply find after taking the cap off it is full of crud. greenish stuff is from no venting and condensation builds up fouling the optical sensor. Careful cleaning will fix opti but the vent harness, if equipped needs to be replaced and confirm at some point no one re-installed it with the blue/white check valves backwards

oil inside Opti will also foul optical sensor but can be cleaned ut. Typically oil enter opti from a bad WP drive seal and or the opti bearing itself. If there is wobble in Opti shaft that typically means the bearing is bad and can introduce engine oil. More common is failed WP drive seal

If Opti is not vented IIRC MSD makes a cap for those that are vented...unfortunately anything LT1 related by MSD is a complete crap shoot. Aftermarket Opti is even more of a crap shoot

 

It is a Delco unit I installed 5 or 6 years ago. It is NOT vented. I would love to be able to test cleaning it, and putting it back in, but thats ALOT of work just in the R&R. Has anybody had luck with this system?

Petris Vented Cap

OR

Petris Complete Unit

Given a new AC Delco unit is nearly impossible to find and Re furbished are already close to 400 with shipping....

Thoughts?

 

So I did some digging. Remember, this car was at the paint shop for about 3 months. I started looking through some of the progress photos. IT spent a Month outside with no hood, bumpers, fenders or quarter panels. I have a feeling this is all due to sitting in the elements.

 

convert it to vented cap

IDK if the Petris is an MSD clone kit or one they just sell but it is cheaper than the MSD ventless to vented Opti kit

You can clean the sensor and inside of your current opti. That original AC Delco Mitsubishi sensor is gold

Use dialectic grease on the large O ring on cap to opti base

 

Update, Either at the Paint shop or the Mechanic's shop the car caught fire. I found a burnt wire harness, and what turned out to be fire extinguisher powder in several nooks and crannies. I had been all over this car before Paint and I KNOW there was not previous Fire damage. Unfortunately it has been to two shops since, one to replace the Fuel pressure Regulator and one to replace the Flywheel.

 

EMC Z28,

As the former owner of an LT-1, I would suspect that the water and/or extinguisher used in the fire has now put your OptiSpark into the grave. Old fuel did not help, of course, and the junk in the fuel system shows poor maintenance.

FWIW, you can get ethanol-free gasoline in the USA in lots of places now, but it may cost an extra US$ .25 or so per gallon. Check for correct octane values:
Ethanol-free gas

 

I would say the fire was definitely the cause. The cap looks like it sustained ALOT of heat. And it is NOT a delco unit. (But thats another head scratcher)

 

I installed the MSD Pro-billet distributor around 15-20 years ago and haven't had any problems. I believe it was the 83811 that is vented. I'm curious what you end up going with. So hard to know the best route when OEM factory parts are nearly impossible to find. I saw on Amazon a remanufactured ac delco professional for around $350. It didn't look like it came with cover.

 

ECMZ28,

Good luck and I hope you can get it running again. I too will be curious to find out if it was the Opti.

 

Just curious….. you said you had four codes, related to the Opti and ICM. In response, in post #2 I gave you a link to Shoebox’s Opti diagnostic writeup, and suggested the diagnostic was required. Did you ever follow up on that? If so, what were the results. If not, why not?