I have an ignition issue with the 2.5 L4 DIS ignition.
Initially I was working to correct a missing problem under load. Typically this is a sign that the MAP sensor is starting to go out. I had no codes so it hadn't died yet but since I keep a spares around I went ahead and changed it. No dice. Problem still remained. Since I hadn't changed plugs and wires for a few years I went ahead and dug into the spare parts reserve and did the whole works.
All parts were new:
Plugs Wires O2 Coils ICM Crank Pos
The old crank sensor had a crack in the barrel - changed for new. ICM replaced. Used Arctic Silver to facilitate thermal transfer from both the ICM and the coil shield. Everything was installed and dielectric grease used as needed where applicable. I didn't clear the ECM but didn't figure that would make much of a difference.
Started right up after all was re-assembled. Ran no-load for about 15-20 minutes to make sure it was up to temp. Shut down engine to finish getting the air filter and a few other small things re-installed. Came back to it a cpl hrs later to do road test. Started right up but as soon as it was put under load (put it gear and let clutch out) it died and would not restart. Acted like I had no spark.
Couple days later I changed out the new ICM for the old one, left everything else as I had it, cleared the ECM and re-started. It ran no load for about 5 minutes then it shut down and would not re-start.
So the question is, after following the FSM instructions and being very methodical about this, what did I miss?
First thing to check is to verify if you are getting spark. Use a spark tester or a timing light to check. If no spark, the ICM or a coil may be bad. If you have spark then move on to checking the fuel supply.
⚠️ Do Not use Arctic Silver or any other Heatsink/Dielectric "Grease" w/ DIS ICM. They will not flow properly for a huge area to spread out. Silicone Grease has same problem as HSG. Si Oil is part of many HSG that "dries out" and using just that will run out fast. ⚠️ Never use "Liquid Metal" that Eats Aluminum!
Use a small amount of Permatex Brake Grease or Nothing. GM installs them Dry but Duke's DIS location make easy to get water and then "rust" in the gap and PBG stops water and act as HSG w/o particles that can cause problems here.
Do Not use anything on the Shield for the Coils. You Don't want Heat from the Coils transferred to the ICM.
Pull the console to allow more air to cool the ECM. Very Careful Use inverted canned air as freeze spray may work too. If helps some to a lot then = "Dead" ECM. See my Cave, ECM Heat
For DIS Duke and some others... While ECM has no control or feedback of EGR, any problems w/ EGR can cause "Ignition Breakup" under load because ECM PROM is written for proper EGR function.
Note: If Heater Joint under the intake manifold is leaking... Coolant is very conductive and can cause problems for the DIS brick. See my Cave, Heater
------------------ Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should. (Jurassic Park)
First thing to check is to verify if you are getting spark. Use a spark tester or a timing light to check. If no spark, the ICM or a coil may be bad. If you have spark then move on to checking the fuel supply.
Since it actually ran after I did all this, I don't think spark is totally the problem unless the ICM did or does a thermal shutdown. I've checked it with an inductive timing light and although it is hard to see it appears that I'm getting some spark. As far as fuel It was running fine before all this and unless the fuel pump is fixing to go tits up (it's only about 4 years old and when it died last time it was just dead not any warning) of course I can check it again but for now it sounds like it always has and pressure (from the sound of it) come up like normal..
[This message has been edited by Mark_j (edited 07-08-2022).]
Did you also remember to swap the shield? See ogres cave DIS ignition. Maybe you got a bad cam sensor out of the box.?
It's part of the ignition brick, why would I not transfer it? Bad crank sensor? Possibility but then it wouldn't run to begin with if that was the case.
It's part of the ignition brick, why would I not transfer it? Bad crank sensor? Possibility but then it wouldn't run to begin with if that was the case.
⚠️ Do Not use Arctic Silver or any other Heatsink/Dielectric "Grease" w/ DIS ICM. They will not flow properly for a huge area to spread out. Silicone Grease has same problem as HSG. Si Oil is part of many HSG that "dries out" and using just that will run out fast. ⚠️ Never use "Liquid Metal" that Eats Aluminum!
Use a small amount of Permatex Brake Grease or Nothing. GM installs them Dry but Duke's DIS location make easy to get water and then "rust" in the gap and PBG stops water and act as HSG w/o particles that can cause problems here.
I actually used the little packet of thermal grease that came with the new ICM and spread it acrossed the entire surface of the ICM and from what I could tell when I changed out the part for the original ICM it had made full contact with the surface. But if that stuff isn't right then I'll clean it all off and use PBG.
quote
Originally posted by theogre: Pull the console to allow more air to cool the ECM. Very Careful Use inverted canned air as freeze spray may work too. If helps some to a lot then = "Dead" ECM. See my Cave, ECM Heat
That would be a recent development and besides wouldn't the ECM give me an indication of something like that when put in self test mode?
quote
Originally posted by theogre: Check Fuel Pressure. Need an adapter. See https://www.fiero.nl/forum/Forum2/HTML/146121.html Pump or other things can F'ed pressure after running, stay running then park and die, and more.
Again, I'll check it, but as I said before, everything was fine until I changed out the ICM.
quote
Originally posted by theogre: For DIS Duke and some others... While ECM has no control or feedback of EGR, any problems w/ EGR can cause "Ignition Breakup" under load because ECM PROM is written for proper EGR function.
Ok, that is a new one on me.
Though it might make sense. According to my records, I changed the EGR some 15yrs ago when I first bought the thing. And the reason I did that then was not because it ran poorly but because I had an Olds Cutlass Ciera with a 2.5 that loved to trash EGR valves. Probably put 2 of them on that thing for the 10yrs I owned it.
quote
Originally posted by theogre: Note: If Heater Joint under the intake manifold is leaking... Coolant is very conductive and can cause problems for the DIS brick. See my Cave, Heater
Not a chance. I'm a fanatic about coolant/fluid leaks and would have caught that one immediately. It still annoys me that I haven't been able to keep the valve cover from oozing oil into the plug sockets. Had a buddy who used to work on Navy P3's with the turboprop engines and his favorite saying was "if it ain't leakin oil, it's 'cause there probably ain't none in it".
The Duke is sorta like that.
Anyway, thanks for the info. I'll let you all know how it turns out once I dig into it again.
[This message has been edited by Mark_j (edited 07-09-2022).]
Nothing surprises me as far as automotive stuff goes. I've seen over the years some real, if you'll excuse the expression, "redneck engineering' that makes one wonder how they get it to even work.
⚠️ Do Not use Arctic Silver or any other Heatsink/Dielectric "Grease" w/ DIS ICM. They will not flow properly for a huge area to spread out. Silicone Grease has same problem as HSG. Si Oil is part of many HSG that "dries out" and using just that will run out fast. ⚠️ Never use "Liquid Metal" that Eats Aluminum!
I've used thermal conductive grease on the plate where the ignition module mounts without problems.
Originally posted by Mark_j: That would be a recent development and besides wouldn't the ECM give me an indication of something like that when put in self test mode?
ECM does Not go into a "Test Mode" or even a "Limp Mode" for most things. Won't even set "Codes" for many problems unless the "Error" follows whatever rules GM has programed for many "codes." And if you get "Limp Mode" operation, only last for rules met to keep MIL On.
Example: You can unplug VSS and drive for hours to days and never see a flash of MIL light or find stored "Code" 24. More so if you have only City Drive to work and things like that.
ECM can barf all over engine timing when have iffy/bad EGR of any type. Bad Valve, Intake Man EGR ports Plugged w/ crap, bad Ported vac line, etc. EGR and Other Vac problems can fail and see no High Idle or set Codes either depending what line and how bad the problem is.
See No Light from Timing Light can be a iffy light or a real problem. Old Xenon Flash units often die from old age. Tube itself can leak gas or other things get old. Inductive units use big Capacitors that can have same death problems as any old electrolytic cap. The pickup for them often has problems making a dim/no flash too. Get any ignition tester that emulate a spark plug. connect to a plug wire and ground to the head. Testing just "holding a wire to ground" can Fry a Coil when the gap is too big. Worse for DIS coils but many other ignition coils can "short out" and flash over when fired w/ big gap, bad wire, etc.
If DIS ICM came w/ "Grease..." what color? Somewhat clear is just plane silicon grease. While can work but not the best. And who sells that w/ grease? Because Wells and Standard that makes ACDelco parts don't give you grease for this ICM.
Many other HS Grease will not flow right for DIS no mater how many say will work. When that happens the ICM can flex and stress the board in it and die at random time later w/o warning. DIS ICM heat area is several time the area on most current PC CPU and they have problems problems getting the grease to flow and even clamp loads to mount whatever cooler used.
ECM does Not go into a "Test Mode" or even a "Limp Mode" for most things. Won't even set "Codes" for many problems unless the "Error" follows whatever rules GM has programed for many "codes." And if you get "Limp Mode" operation, only last for rules met to keep MIL On.
Let me get this straight.
The ECM does not have a "self test" or "error" function and
Code 12
Diagnostic Mode Active (ECM OK) When the diagnostics terminal is grounded, the ignition turned on and the engine is not running, the ECM will flash Code 12 three times. If it's flashing this code while the engine is running (Field Service Mode), then the ECM is not receiving any pulses from the distributor.
and
Code 55
ECM Failure Check all ground connections of the ECM. If all are ok, replace ECM.
Mean nothing?
quote
Originally posted by theogre: can barf all over engine timing when have iffy/bad EGR of any type. Bad Valve, Intake Man EGR ports Plugged w/ crap, bad Ported vac line, etc. EGR and Other Vac problems can fail and see no High Idle or set Codes either depending what line and how bad the problem is.
I got that. Obviously I'll have to check the EGR system to make sure it functions like it should including all the support vac lines.
quote
Originally posted by theogre:See No Light from Timing Light can be a iffy light or a real problem. Old Xenon Flash units often die from old age. Tube itself can leak gas or other things get old. Inductive units use big Capacitors that can have same death problems as any old electrolytic cap. The pickup for them often has problems making a dim/no flash too. Get any ignition tester that emulate a spark plug. connect to a plug wire and ground to the head. Testing just "holding a wire to ground" can Fry a Coil when the gap is too big. Worse for DIS coils but many other ignition coils can "short out" and flash over when fired w/ big gap, bad wire, etc.
When I spoke of it being difficult to see it was because I checked it in bright sunlight while wearing polarized sunglasses. I never look directly at Xenon flash units even on timing lights through the diffuser. It creates "spots" on the retina that take a while to dissipate (think of camera flash from back when people still used film). So it was hard to tell if I was getting reliable pulses through the wire using that method. As far as reliability of timing lights, I have 3 of them. 2 pro grade and one I inherited and I'm pretty certain that all of those lights work properly. What I didn't have at the time was the little Lisle inline tester I normally keep in my service cart. It was on loan when I did this check.
quote
Originally posted by theogre:If DIS ICM came w/ "Grease..." what color? Somewhat clear is just plane silicon grease. While can work but not the best. And who sells that w/ grease? Because Wells and Standard that makes ACDelco parts don't give you grease for this ICM.
White, kinda looked like Lithium grease. Airtech Wells was the part manufacturer. When I disassembled the ignition block the ICM had a greasy tape type stuff on one side and something similar but more like an insulating tape on the shield side.
quote
Originally posted by theogre:Many other HS Grease will not flow right for DIS no mater how many say will work. When that happens the ICM can flex and stress the board in it and die at random time later w/o warning. DIS ICM heat area is several time the area on most current PC CPU and they have problems problems getting the grease to flow and even clamp loads to mount whatever cooler used.
So you recommend non-solid (not the stuff with ceramic particles) PBG right?
Green Label PBG is what I've used for many years. Forgot they have others. They make/made a plastic tube, ~4oz I think, last last most DIY for years. Likely still find in stores even tho Permatex only seem to show the can.
code 55 and many others may mean something or completely bogus. 55 may mean have a bad ECM or any plug(s) don't connect right including 1 pin Reset plug in engine bay or iffy "+ box" under C500 where nearly all power wires end up.
If have Factory ECM, can "die" from heat or known defect w/ how made. If some other things died or people test things wrong then can "kill" an ECM too. "Dead" maybe completely Dead or not. ECM might set 55 but often one function won't work... Example: You have spark and others things seem to work but bad driver circuit to injector won't run fuel injector in TBI. I and few others had this problem. In https://www.fiero.nl/forum/Forum2/HTML/146217.html ECM won't prime or run F-pump because F-pump Driver in ECM was dead.
DIS ICM Should run the ignition when ECM works right because that make spark by itself until ECM sees 500-600 RPM. If have iffy wire(s) between them or Iffy ECM then ECM might not take over timing or control line "shorted" and ICM does not make spark right to start the car.
Save the PROM in the ECM to move that to any replacement ECM.
Had a buddy who used to work on Navy P3's with the turboprop engines and his favorite saying was "if it ain't leakin oil, it's 'cause there probably ain't none in it". 
