Take the vehicle to AutoZone or similar and have them do a full charging system check. It's free.
When you say ICM, do you mean just the icm module or the module with the coils attached?
The bolts that hold down the coils to the transmission case serve as the ground for that part of the system. If there is severe corrosion in the bolt holes or on the bolts themselves, you would suffer from intermittent grounding issues. Your issue seems to be all or nothing, and I wouldn't expect it to only affect cylinder number four, unless that one coil pack is intermittently misbehaving. That would lead to misfires on one and four. This could explain getting a random misfire code because that set before the PCM could figure out which cylinders were involved, and it may not be consistent.
tI've driven and s car on three cylinders for 9 months so I know about reduced power. I don't even know if they can run on to cylinders. I've never tried. So that's one possibility
Normally I would say to swap the coils with each other so that the coil for two and three is used for 1 and 4, but since you don't have a cylinder specific misfire, you can't trace weather the misfire moves to a different cylinder or not.
What plugs are you using? Stock NGK plugs? I might have already asked but I'm asking again anyway. More ignition problems are caused in these engines by not using stock plugs than anything else. Some people have no issues, others have engines that will not tolerate anything besides stock NGK plugs. Pull all of the plugs and check for oil fouling or plugs that reek of gasoline and don't have the nice light brown appearance that they should?
In general I would also suggest you do a compression test dry and wet. If you do not know how, look on YouTube at 10 videos. Seven will be done properly with the gas pedal all the way down, two will almost be correct, and the last will be completely fucking wrong.
Misfires can occur due to very low compression. If you have a valve that's sticking, it may be intermittently low.
Try different devices in your lighter socket to confirm whether it goes dead or the device you're using just isn't making good contact. You can of course always use a voltmeter and touch the back center and the sidewall. Just be very careful not to short the back center to the wall. that will blow a fuse.
Having l headlights blink? Do you mean completely turn off and come back on super quickly? I used to sort of have that going on with my 97 SC2. For example if I braked really hard, the lights would stutter for a microsecond but everything still behaved normally? Are we talking about the same thing?
The only thing I could really see damaging the ICM related to the alternator is if the voltage regulator inside the alternator is not properly regulating the voltage, and something is taking it out when the voltage goes too high. But that is a total guess. The charging system test should expose a bad voltage regulator in your alternator.
Historically there have been troubles with the power distribution on a few of the pins and the instrument panel junction box behind the actual fuse holders. Depending on generation, one of the F pins would have the radio, fuel pump and chime all pulling 12 volts from it. The combination of those devices pulled too much current, heated up the pin, and would eventually melt the contact and scorch the plastic. Sometimes stuff stayed attached, sometimes it didn't. Sometimes only certain things came undone while others stayed attached. You can do a quick visual by removing the left side kick panel that is velcroed on just like the one that exposes the fuses. With a bright flashlight you can see the wires coming into the back of the fuse panel. If there is one that is scorched, you'll see it.
I think there are enough ideas above for now. The loss of power is of course consistent with an actual misfire. The PCM can misinterpret what's going on as a misfire. But if the plug itself literally is not firing, you're going to feel it.
When you pull the plugs for the compression test, ground out the ground electrode part and have someone crank the engine to ensure you are getting a strong spark on each cylinder.
I have an inkling that your issue may lie in the grounding of the coils to the transmission case. It's the only thing that has physically changed between the old module that was presumably bad and the installation of the current module which is misbehaving. I don't know that having an intermittent ground for the ignition coils would definitely cause different cylinders not to fire.
There are other things to check, but that would make this post 375 pages long, and all of it would be speculation, just like most of what's above.
Somewhere we know about what doesn't work and when, the sooner we sort this out. You've been very faithful in reporting things that others would just assume are unrelated but may actually be involved and also be the key to sorting it out.
Thank you.
I think I once played 142 questions with someone who owned an 94 SC2. So much stuff posted, so much information that was in fact totally unrelated, but buried in post 72 was one of the keys to us sorting it out. I don't mind playing 146 questions if it really takes that much. Some of it was spent bitching at the guy trying to get him to do what I recommended. Blah blah blah
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I would do the compression test, they're charging system test, and the visual on the plugs, swap if not OEM, and make sure they are still properly gapped if they've been in there for a while.
