88 2.5 L4 Ignition issue (Page 2/2) theogre JUL 09, 11:32 AM quote 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. Mark_j JUL 10, 10:01 PM quote Originally posted by theogre: 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? theogre JUL 11, 01:47 AM 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.