94 Roadmaster cuts off a few minutes after a cold start/restarts -cel then no cel. ???

I've been trying to diagnose why the engine cuts off for months now. 
Engine cuts off a couple minutes after startup, restarts and acts fine...here's the story of the past couple months.

At first it was after a couple minutes of run time it would cut off. First two times it happened I was coming to or sitting downhill at a light/stop sign.  I was low on gas so I filled up. No change. I was getting a check engine light, code 36. 

Vaccum lines were checked and rechecked, all seemed secure but the bottom vacuum for the opti. There was some slack so I cut off the worn out 1/2 inch section on the end and now all were secured.
At the same time I checked all electrical connections and found one of the three ground cables on the left side of the icm/coil bracket was broken.  Managed to get it tightened down.
No change, still would cut off after a few minutes of run time from a cold start.  Cel with Code 36.
The odd thing is after it would cut off it would usually restart with no problem except with a cel until I went wherever I was going and came out to leave.  When I was leaving to return home the check engine light would not be on and it would not cut off.
This was the standard operating procedure for months, so if I wanted to go anywhere I had to start it up and walk away until it cut off. Then hope it's done cutting off for the day...this is no way to live btw.

Not wanting to throw expensive parts at it just guessing I disassembled the icm/coil/heatsink bracket unit. Cleaned all the dirt, oil and gunk off of it and reassembled everything with heatsink thermo paste.
I just got everything back together.  It fired right up with different but the same results.

Cut off after a minute or so (which seemed sooner than usual)...and cut off a few times at rather quick intervals alter the initial cut off which is different than the single cut off for the last few months.  No cel/codes with the cut offs.  Ran it up to temp and it seems fine apart from the early cut offs. Of course that's kinda how it would run after the initial cut off before with the exception of now there are no cel/codes.

Leaning toward the icm but feeling more confused than usual about it.  Thoughts?

Any help is greatly appreciated. I'm supposed to take this on a couple thousand mile trip in about a month.  Not feeling good about taking this car if it's going to keep doing this.

check the optispark wiring harness from the valve cover down to the opti,. they get corroded and will cause aggravation ,.

If the vacuum hoses are full of condensation,. you'll have weird situations like this,.if you are chasing condensation gremlins in an old opti,. it can be very frustrating,.pull the hoses off intake side and the little one way valve thingy off, and hook a vacuum cleaner up to one of the hoses,. see if its drawing air in the in the other hose knowutimean?

I will say tho,. this is classic opti spark type behaviour when its in its death throes,.,.

might be time for a newer one with some new wires and plugs,.

I've misplaced my list of codes, so I don't know what "36" is.
Check the coil to Opti ignition wire.
After that I'd consider replacing the coil first, then the ICM."Good" quality replacements sell for a total of about $75-$80 at RockAuto.
Both have been known to fail intermittently, and intermittents can be a tough issue.
Another possibility is the temperature sensor for the ECM, which is located on the lower driver's side on the water pump. At least remove the electrical connector and check for corrosion.

paart wrote:

I've misplaced my list of codes, so I don't know what "36" is.
Check the coil to Opti ignition wire.
After that I'd consider replacing the coil first, then the ICM."Good" quality replacements sell for a total of about $75-$80 at RockAuto.
Both have been known to fail intermittently, and intermittents can be a tough issue.
Another possibility is the temperature sensor for the ECM, which is located on the lower driver's side on the water pump. At least remove the electrical connector and check for corrosion.

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Code 36 - ignition fault , high resolution signal

Thanks for the link. I have a printout of the codes that I was using about 3 weeks ago, and don't remember where I put it. I'll find it, sometime.

It's odd that you are getting no CEL now, but the "high resolution signal" is one of two output signals from the Opti. As Phantom309, mentioned if cleaning the electrical contacts doesn't solve it, then it's highly likely that it is the distributor that's failing. Look over the actual wires, right down to the distributor body, just to see if there's anything obvious, such as cracked insulation.

Well I looked around for any corrosion in the electical connections and didn't find any.  

After startup it acted the same as yesterday. Cut out after a little while then a few times quickly after.  No check engine light either.  Went for a drive after the troubles were over and she acted just fine, ran smooth, got up when I told her to and didn't have a hiccup.  No cel before or after...except in the accessory key position so the light does work.

Can anyone confirm if those check valves on the vacuum line from the opti to the intake are absolutely necessary.  The larger one seems to not allow much air through.  Is that line something that is best or even available as a complete unit or just some hose by the foot at the parts store?

As far as plugs and wires.
Plugs were done probably a year and a half ago and the wires were done about this time last year. So they're pretty fresh.

They're just standard vacuum hoses. I replaced all mine with silicone ones. You don't need much air flow through there. One thing to check is to see if the cap and distributor are actually sealed. My opti was leaking badly through the main shaft bearing, so it was sucking crankcase vapor through it instead of clean air.

Also don't discount pulling the plugs for an inspection and reading. You can learn a lot just by looking at their condition.

There are two valves in the vacuum line to the Opti. The one closest to the intake is a check valve. The larger one further down the line is a check valve/filter. I've not tried it, but I'd assume they could be cleaned out with mild solvent, such as mineral spirits.
The FSM states that intake manifold vacuum in the distributor will cause a misfire. I'd guess this would be the result of a clogged air supply hose (from the air cleaner) and maybe faulty check valves. This vacuum would probably draw oil through the bearing into the distributor.

For what it's worth, the FSM also states that the hi-resolution signal from the distributor is not necessary for the engine to run. I have no idea what to make out of that statement!

Still the same symptoms.  Runs fine on startup then cuts out, once or possibly a few times after until warm.  Not getting codes on the cut offs, just turns off.

Runs fine when warmed up though.

Everyone loves to say it's the opti (you guys must have stock in opti suppliers) but I've only ever heard of an opti problem getting worse when warmed up.

The search continues.

Well this car has been a paperweight since about new years and it's time to get her rolling again.

Last july I did the coil, icm and everything seemed fine. Went on a trip of about 2000 miles without issue but around the time summer was ending the problems had returned. By Nov/Dec it was unreliable and not safe for family transport.

Unless the car is cursed it looks like an opti replacement. What parts and tools will I absolutely need? I've been down the internet rabbit hole and I feel like I've learned some but may have come out more confused.

Anyone familiar with [You must be registered and logged in to see this link.] The kit is pretty expensive but they do sell just the opti. With there not being any new Delco opti's available is that opti a good way to go? How about the kit with everything?

There's really only one part that can fail in the distributor, and that's the optical sensor. Assuming of course there's not some physical problem or if the rotor/cap is worn out, or it got soaked with coolant, that sort of thing.

You need to remove the water pump and balancer to get the distributor out. You probably will want to replace the oil seal also.

What you do is a toss up depending on if your time/labor or your money is most valuable.

All the aftermarket distributors have cheapo sensors which have a very poor reliability track record. Though I would trust MSD's quality in this regard over some others, including Accel which I tested and found to be lacking. If you swap in a modern aftermarket unit it should live long enough to tell you if that was the problem or not. I would skip the ones that are selling for $100 or less though.

Maybe someone here will sell you a known good used unit that you could swap and at least make the same conclusion.

There are NOS distributors and refurbs out there, but you probably won't get one for less than $400 if recent history is any indication. GM/Delco part number is 1104032 if you want to call around the dealers and see if someone has one.

Upon further investigation it seems that MSD also uses the same aftermarket sensor, so your results may vary there.

I have no experience with Petris but they seem to back their distributor better than any other aftermarket unit I've seen.

Again though, any mid-range unit should work at least long enough to determine if the distributor is the problem or not.

Also let me know if you're going to toss your old distributor. I can use some carcasses for experimentation.

This lazy susan is dirty.
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Trying to end this saga.

Went with a reman ac delco opti. Sorry lamune the core charge was hefty so I'll be returning it, unless you want it for the core charge.

I wasn't planning on doing the water pump but after I looked at it and saw the bearing cover barely hanging on...it was time.
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Went ac delco as well so it came complete with a new thermostat.
Wasn't planning on replacing the harmonic balancer either but the rubber was badly cracked and an area was separating. I needed this back together quickly so I went to the local parts house.
Assembly went alright, remember the correct order things came off so you don't go two steps forward and three steps back in reassembly. Space is limited even for a full size car, a garage would of been helpful.
Got a new battery because I took the roadies batt out when it didn't run for my truck.
Hosed out the coolant tank which was harboring chunks of who knows what. If anyone has a good 95-96 tank is be interested because my 94 has the dual hose on top and I'd like to not have to plug the unused outlet.

Threw some coolant in and she fired up on the first shot.
However...now after all this the ac compressor and the secondary fan will not come on for anything. No number of battery pulls nor fuse and connector checking will make them kick on.
Thoughts?

In my experience the Secondary fan won't kick in until it's hot enough. And I mean HOT.

I assume one fan is at least turning once you turn on the AC.

Is this a Towpack car with the mechanical fan or normal with two electric.

To test I would pull the thermostat connector from the water pump after you start the car. Be careful of the accessory belt and the fans. It will set a check engine light and put both fans to full speed.

Then re connect and it should go back to normal function.

I typically do this once a year just to make sure the fans run correctly.

It's a tow pack so only the mechanical runs. The compressor wont kick on nor the fan. I did pull the sensor out, the codes flew and the fan does work.
At on point in the line of battery pulls the radio wouldn't come on, it displayed a station but no sound and the clock was read triple 000. Which is something i have never seen before.

Thanks for thinking of me!

If it's got a core charge, don't worry about the opti, I don't need one that badly. I need to get the bench cleaned off so I can build a test rig and who knows how long that'll take. Have a bunch of backed up projects already.

Did you change the opti and WP seal while you were in there ?
I generally like to open the replacement optispark and loctite the screws on the rotor, then reseal it with a thin bead of black RTV. I also like to put some shrinkwrap on the opti electrical connector. Like nick said, they have been known to cause problems.
I think one of our members here sells elbows to put in the WP weep hole to prevent it from subsequently leaking into the opti in the event of failure. I've never had one on hand when the WP was out, so I just seal the opti.

jasonlachapelle wrote:

Did you change the opti and WP seal while you were in there ?
I generally like to open the replacement optispark and loctite the screws on the rotor, then reseal it with a thin bead of black RTV. I also like to put some shrinkwrap on the opti electrical connector. Like nick said, they have been known to cause problems.
I think one of our members here sells elbows to put in the WP weep hole to prevent it from subsequently leaking into the opti in the event of failure. I've never had one on hand when the WP was out, so I just seal the opti.

Yeah, I did the seals while I was in there. The opti came with the plug already shrink wrapped to the opti. Should of taken a pic of it before installing.
Thought about doing the loctite on the opti but I went with the delco reman and am hoping they learned how to seal these in the last 25 years.

Just racked up 1000 miles in less than a week (basically two days of travel) and she is running good, except still no ac or secondary fan.

It is possible to hook up both fans in parellel, so they both go on at the same time.

You can run a jumper wire from the signal input of fan relay 1 to the signal input of fan relay 2.
They will both come on when the first fan relay sees the signal from the ECM, and it passes to relay 2. You can check operation of fan 2 but disconnecting the harness as it comes away from the fans, as it comes up onto the fender well (passenger side.) By runninga ground to the black wire. You can take a second wire from the battery to the individual fan wires to power them up to check if they work.

on both roadmaster with mechanical fans that I owned, the 2ndary fan was U/S

What does U/S mean?

unserviceable