ICM Issues

[2seater]

The engine starts on commands from the ICM and then switches to ECM control of the timing after it starts. I think the problem lies in the wiring between the ICM and ECM or the PROM and ECM combination. The two common elements which have not been replaced is the wiring and the PROM. Checking the wiring for continuity or cross talk is straightforward with an Ohmmeter and a long jumper wire. It can be done alone but a helper makes it much easier. The color codes at the ICM and the ECM are the same and am pretty sure all the relevant connections at the ECM are in the 32 pin black plug. A loaner Prom and/or ECM w/Prom as well as the wiring check have been suggested before.

[Padgett]

Runs for a second and dies sounds more like a fuel issue. What is the rail pressure doing ? Needs to be at least 30 psi.

[Alchemy333]

3 hours ago, Padgett said:

Runs for a second and dies sounds more like a fuel issue. What is the rail pressure doing ? Needs to be at least 30 psi.

I just lost a lengthy response. I feel there may be multiple issues which makes it difficult to narrow down to one. In short I will be addressing a potential fuel issue and overhauling the rail and injectors next regardless.

 

I went ahead and threw the old ICM in again... and it runs, same as it always has,, with the miss. In observational thought on why 3 new ICMs won't run... is the original was designed to operate in a limp mode if the ICM was not communicating with the ECM. What if the new designs no longer contain this ability? That would narrow it down a bit... and also explain a fuel delivery issue at the same time.

 

I did contact Flagship One about their plug and play ECM with prom. They stated it dosent matter what PROM because they remap it appropriately to State and VIN. They quoted $499 with a lifetime warranty... last resort. Still a chunk of change though.

 

At the end of the day, I can't really assume anything that the last guy working on this thing may have tried or been thinking... i.e., it contains a previously remanufactured ECM.

[Alchemy333]

Put her back together and drove her around a bit. She drives very nice aside from the miss/slightly rough idle with old ICM. Will pull the rails and injectors over the weekend and see if it helps. No noticeable issues while driving. ABS light still on too, but otherwise stops as it should. New struts feel nice too... but needs alignment.

[2seater]

While it is operational, do some of the tests suggested to see if the cylinder(s) giving trouble can be identified. I don't think the ICM's would have any features removed. Why they don't work is unclear, but while it is operational, check the things that you can. Then perhaps swap in one part at a time if desired. Just go through diagnostics and write down each reading as you step through the ECM data while it is idling. Maybe something will jump out??

Make doubly certain the spark plug connections are in the correct order. It is very easy to switch two of them on the rear bank. It has caught out many before you.

Edited April 22, 2023 by 2seater

[Padgett]

Jim Finn or Maark probably has a known good Delco. Think I paid $40 at a yard for a my last one complete with mounting plate.

[Alchemy333]

So, I replaced the injectors couple days ago, and ran much better. Drove about 4 miles yesterday with no issues. I was scheduled for an alignment today and go to start it up... Started rough and has white smoke that smells like gas... running really rich. Do I try another iCM? ECM? FPR? bad injectors? I was going to grab a fuel preassure Guage today and didn't get that far.. This is getting frustrating as I thought I may have narrowed the misfire at idle situation to the PCV. Of course I'll be testing spark to plugs today... but, just wondering if this is something anyone is familiar with otherwise. To recap a bit,, ive been running the original ICM. Thanx.

Edited April 29, 2023 by Alchemy333

[Alchemy333]

May have answered my own question. Pressed the Schrader valve... and there was zero release. I hear the fuel pump pressurize... so I can only assume a faulty Fuel Preassure Regulator. Interesting it would run rich with no fuel preassure though... or run at all... ffs

 

Edit: could be an injector stuck open though. Would that just dump all preassure into 1 cylinder. I tested valve while running and not running... same results of no pressure/fuel released.

Edited April 29, 2023 by Alchemy333

[Ronnie]

33 minutes ago, Alchemy333 said:

I hear the fuel pump pressurize...

What does fuel pump pressure sound like?

[Alchemy333]

3 minutes ago, Ronnie said:

What does fuel pump pressure sound like?

It preasurises as usual and stops as usual

[2seater]

The pump runs to pressurize the fuel rail for just a few seconds and then times out. It does not have any form of pressure sensor to turn the pump on and off. While the engine is running it runs continuously. If the engine runs, and can be driven, there must be a minimum of 30 psi or so in the rail. It may bleed off right away from a faulty fuel pump connection in the tank, bad check valve or leaky injector. I thought fuel pressure and pump was checked way back in the beginning?

[Alchemy333]

45 minutes ago, 2seater said:

The pump runs to pressurize the fuel rail for just a few seconds and then times out. It does not have any form of pressure sensor to turn the pump on and off. While the engine is running it runs continuously. If the engine runs, and can be driven, there must be a minimum of 30 psi or so in the rail. It may bleed off right away from a faulty fuel pump connection in the tank, bad check valve or leaky injector. I thought fuel pressure and pump was checked way back in the beginning?

I got preassure again. Replaced the ebay specials with GP Sorensen's. But, now I have fuel in my cat. Not sure if I just run it out or if I destroyed the cat. Has a little hesitation and smoking from behind the engine a bit... dripping from cat a little. Ran for 3-4 min and blew alot of white/grey smoke out the back... which diminished. I dont have a fire extinguisher on hand... if that could possibly happen.

Edited April 30, 2023 by Alchemy333
No codes

[Alchemy333]

Took it for a drive anyways. All the smoking subsided.  She now runs better than ever has. Smooth driving and quicker acceleration. Still got a bit of a rough idle, but its better than before. The exhaust smells cleaner too.. The diagnostics now read both no E codes or B codes. 3 R codes are all I got yet to deal with. I may be expecting too much from a car of this age... idk

[2seater]

2 hours ago, Alchemy333 said:

I got preassure again. Replaced the ebay specials with GP Sorensen's. But, now I have fuel in my cat. Not sure if I just run it out or if I destroyed the cat. Has a little hesitation and smoking from behind the engine a bit... dripping from cat a little. Ran for 3-4 min and blew alot of white/grey smoke out the back... which diminished. I dont have a fire extinguisher on hand... if that could possibly happen.

Are you referring to the injectors? I imagine that is the oddball long tail version are gone? I am glad it is working better but the whole affair has been very confusing. 

[Alchemy333]

1 hour ago, 2seater said:

Are you referring to the injectors? I imagine that is the oddball long tail version are gone? I am glad it is working better but the whole affair has been very confusing. 

Yah... returning those guys. Its pretty apparent that one must have got stuck open. Im looking at 2 things that could be giving me the "not as smooth as it should be" idle.

 

1. Judging by its location, the PCV valve is most likely over due for replacement.

 

2. I have a rattlish intermittent knocking top back of the engine, which sounds to me like a balance shaft issue. Not sure if a new timing chain and tensioner (most likely also over due) may resolve this... or even if the cause for my idle issue. 

 

Car has 107k mi.

[2seater]

At 107k miles, it shouldn't have worn out mechanical parts. The balance shaft sits in the center of the engine just above the camshaft and is driven by a toothed gear directly from the camshaft. No chain involved. A rattle/knock can mean different things to different people. A failing harmonic damper will usually manifest itself as a knocking sound at low rpm the goes away at increased rpm. Feel the face of the damper for cracked or missing rubber. It should be completely smooth. Rattles can come from anywhere, especially loose heat shields on the exhaust and firewall. Use a mechanics stethoscope or even a wooden dowel to listen to suspect areas to try to isolate the sound. Maybe something in the valvetrain in the rear valve cover? Long term unprepared storage can lead to sticking parts.

 

The PCV valve is pretty reliable. Beware of hardened rubber grommets if trying to remove it. 

[Padgett]

" I dont have a fire extinguisher"  Water is no good to gas/oil fire. Smothering may work. At last count I have six large and two small (carry in car).

[Alchemy333]

8 hours ago, 2seater said:

At 107k miles, it shouldn't have worn out mechanical parts. The balance shaft sits in the center of the engine just above the camshaft and is driven by a toothed gear directly from the camshaft. No chain involved. A rattle/knock can mean different things to different people. A failing harmonic damper will usually manifest itself as a knocking sound at low rpm the goes away at increased rpm. Feel the face of the damper for cracked or missing rubber. It should be completely smooth. Rattles can come from anywhere, especially loose heat shields on the exhaust and firewall. Use a mechanics stethoscope or even a wooden dowel to listen to suspect areas to try to isolate the sound. Maybe something in the valvetrain in the rear valve cover? Long term unprepared storage can lead to sticking parts.

 

The PCV valve is pretty reliable. Beware of hardened rubber grommets if trying to remove it. 

Yah... I had the harmonic balancer noise too... so replaced it with new. I changed the oil with the purple synthetic (brand name fails me atm)... and had a lil room for half a quart of marvel mystery oil yesterday. It's possible she may just need to be sent on a good run too. I'll check the heat shields... but sounds pretty internal. Not a ticking or a piston slap sound or symprom. If it doesn't clear, I'll pull the valve covers and check rockers too. But, it's pretty intermittent. The old injectors were clearly a factor.

 

As far as PCV... ive never worked on a car where it was ever dysfunctional... always they rattle. But, most cars ive dealt with have them more readily accessible for inspection and service. Its a cheap maintenance item... but, im not messing with it until I can locate the appropriate grommet. If the grommet is completely deteriorated (sight unseen atm) it could be a source of vacuum leak too. No?

 

If I make any new discoveries, ill post it here. My ABS light still hasn't gone off yet either... and the whole system is new/replaced except the 2 rear speed sensors... but brakes are operating pretty solid so just gonna keep it on the back burner.

 

Appreciate your guys help. Thanx!