Your perseverance will pay off. Good luck, you can't be the only guy with this type problem. Please keep the posts ccoming.

It'* a man-eater. This thing is going to drive me to drink. I was just sure that it was a bad ground. But I haven't found it yet.
I checked and cleaned/polished all 4 in the engine bay that the book shows; G100, G102, G103, & G104.

Also did G202 & G203 in the interior on each rt & lt. kick panel.

I got excited to find the G100 loose (the one between and slightly below the ICM and alternator. I think this might be the one to the ICM... or not). The outer nut was tight against the inner one, but not the inner one, that counts.

After cleaning, I haven't gotten a code yet. But I'm not getting suckered like yesterday. It still has that crappy spot in throttle-up. So, I'm going to let it cool and repeat yesterday'* maneuvers to see what happens. Still thinking the dead spot is tied to it somehow. Tomorrow is last day before surgery and recovery time.
News at 11.
Manic in Memphis

New observation.
The latest little test is still NOT showing any codes, but I noticed something with the lights on and all (first time in the darkness for a while).

When I stab the gas and hit that crappy spot, the lights dim slightly. If I rev it gradually, voltage seems unaffected. This is a chicken and the egg thing; which is causing which...

If the voltage is dropping at that rough spot, no wonder I was throwing codes. But what the heck is causing this weirdness? You would think it would be just the opposite

I will check the connections at the alternator tomorrow evening and any ground straps I can find. Maybe the B+ cable too. I feel like we're getting closer. If anybody can think of something else, please advise. Maybe a ground somewhere I missed.

Thanks
"Dirty ground bad. Clean ground good." (trying to sound real philosophical)

My 1993 SSEi used to do that very same thing (kinda like it hits the "wall" when you fully stab the gas when cold). And Boozes 1993 SSE did the same thing when cold IIRC.

From the sound of things, the coil packs are drinking up juice that the alternator or battery can't put out fast enough. But...that "dead" spot" shouldn't be a part of that. Let'* try this....unplug your MAF sensor, then start the car and do your tests. The PCM will default to stored-in values and will throw the MAF code. In some cases, the idle and throttle reponse actually improved when this was done (showing that the MAF sensor itself has gone bad). Have you cleaned the MAF sensor yet? The wires could also be dirty on the inside, giving false readings to the PCM.

No, I have not tried cleaning the MAF sensor. I read where it is downstream from the throttle body, so I guess that has to come off first. Is this a relatively quick thing? I don't have much time tonight because of loose ends to tie up before I have surgery tomorrow. Can I clean it with carb cleaner?

Oh, and better clarify my "crappy spot." It is not something you can accelerate through. Once it goes to sputtering, which is immediately, it stays that way as long as you have your foot in it. You can pretty much feel/hear it missing and really not clearing up, maybe even getting worse the longer you hold it.

I'm going to also check with that friend of a friend to see if he'* ever heard of the voltage drop thingy. I agree, the coils are the only thing I can think of that would draw extra current.

I have theorized that some/all electronic ignitions boost the spark voltage when you accelerate hard. I had a V6 Ranger once where a plug wire was breaking down and arcing out only if I nailed it. That is where I got to thinking this way. If that is so with Red Sled, could one of the coils be arcing internally just when I gas it? Don't know if that would throw a different code, though. Just a thought. I don't know if it would show up on one of those in-line (neon) spark testers. Something I could try. If it were not for the rain here and early darkness, I could drop by the yard on the way home and grab a bag full. Pansy.

Anyway, after today, I may not be able to post for a couple of days. And may not be allowed to work on it for a couple weeks (which will drive me crazy ).

Thanks for the ideas and the continued support.
BTW, Red Sled looks like a twin to the small graphic at the top right of this forum page. When I get through this, I'll give her a beauty treatment and snap some pix.
Raining in Memphis

PS On the suggestion by one of the other members to also snag an ICM wiring harness; I tried to, but the doner vehicle was so high off the ground (on blocks) that I couldn't get at the back wires; plus it was ugly and I was beginning to freeze my hiney off. Double pansy

Do NOT use carb cleaner. Any auto parts store should have CRC MAF sensor cleaner. There really isn't anything to take off of the car except the sensor itself. It is the black box looking thingy on the throttle body, and it has 3 screws that hold it in place. Taking it out, cleaning it, and while you have the sensor out, spray inside the TB cavity with TB cleaner.

Don't worry about the surgery...I went through double hand surgery a few times, and I still found myself posting on here...albeit I was hunting and pecking around

I cleaned the MAF sensor and it was a major improvement... probably 70%. A 10 mile test drive exhibited no problems, other than still some problem with the crappy spot; but still much better. Backed her into the garage and revved it a couple times; then the stinker threw a code 42 again.

Have some things I may try after I can work on it again. Just in 2nd day of recovering from abdominal surgery.

BTW, am assuming that coolant leak below the TB is not associated with this. Later

I'm back on this one after fixing the coolant leak. On the test drive, if I took it nice and easy, it seemed fine. But on the return loop, warmed up, the old "crappy spot" was noticeable and I got the 42 back, just driving.

As erratic as this is, I'm headed to the salvage yard Sunday and see if I can find a decent ICM wiring harness.
*I still need to check B+ cable and alternator wires (headlights dim when I rev the engine at the same time as I hit the "crappy spot.")

Is there any need to zero in on coils or O2? The low mile O2 on there is likely a Bosch.
Also, is a resistance test on these dependable?

To pull everything together, here is what I have done so far:
1. Rplcd ICM
2. Rplcd Cam Shaft Sensor
3. Rplcd Crank Shaft Sensor
4. Cam magnet in place
5. Used PCM w/old chip displayed same symptoms
6.Clnd/polished underhood grounds and kickpanel grounds (G100, ..02, ..03, & .. 04, G202 & 203)
7. Clnd MAF sensor w/ CRC MAF cleaner. (helped some)
8. #6 or 7 seemed to help the code 18.
9. Ground at cam sensor connector pin B
10. Ground at crank sensor connector pin C
11. 11 V at cam sensor connector pin C
12. 11 V at crank sensor connector pin D
13. 5 V at cam sensor connector pin A
14. PCM connector (unplugged)
>BA6 & BB6 (PCM Ground) Grounded
>BC8 (wire 453) Grounded
>Key "ON"
>BA12 (wire 630) 5v
>BC11 (wire 430) 5v
15. End-to-end Continuity check w/ ICM & PCM unplugged good for
ICM pin A to PCM pin BC7 (ckt 423)
ICM pin B to PCM pin BC6 (ckt 424)
NOTE to SELF: Ensure neither 423 nor 424 is shorted to ground

This clue is too important to ignore. The headlights dimming right at the trouble spot must be significant. What would cause that? Battery, alternator, wiring ? Or (if you had not already done the whole car) a bad ground. Re the chicken and egg, I would guess that low voltage is causing the rough spot, not vice versa.

Therefore, I would be taking a real close look at those battery cables and alternator wiring. Internally corroded battery cables have caused lots of "starts fine but suddenly stalls" complaints here. You have to cut or peel back the insulation on the end to find the corrosion. (I cut mine to check them....they were nice and shiny inside. I covered them with dielectric grease and cable-tied the molded end back on.) Most common point of corrosion is the positive cable near the battery. Others have reported problems similar to yours that finally disappeared when the cables were replaced.

If the cables can be eliminated as a possible cause of the problem, then I would be looking at the battery itself and the alternator as long as that dimming symptom persisted.

I would not trust a resistance or even a scan tool test on an old O2 sensor. And if it is a Bosch...even though it is low miles..., I would just replace that with an AC Delco.

Latest News: (Sorry these posts are so long)
Making headway and discoveries, but still not fixed.
B+ Cables:
For good measure, I cleaned, polished and greased the 2 big + cables
At
Battery
Starter,
alternator and
Vehicle B+ at the firewall fuse & relay center*
*I thought this was the problem because the 2 metal buss had electrolysis corrosion. I separated, polished and greased it up good. NONE of this resolved.

ICM (Ign. Control Module) Connector - I/we have been suspecting something on this all along and I have tried tightening the female pins. Today I figured out how to test it a little better.
I used a #73 drill bit to check/compare tightness/fit of each pin with relation to the others (with the plug off, of course).
About 1/4 of them are loose. Yup, you guessed it, pin A, white wire, that can cause a code 42. Also, M, N, (crank & cam sensors) and P +12v IN.
All this, I am sure, would cause all the symptoms (code 18 & 42) and esp. when voltage drops. All theory, though. I tried closing the pins down more, but didn't help. I'm still trying to find a connector (can't make it to the yard until tomorrow).

Part of the problem with the voltage drop with lights on when I stab it (I could drop it 2volts by stabbing it about 8 times repeatedly).... was the IDLER PULLEY! I witnessed it "jumping" when I stabbed it. The bearing was getting loose. New one doesn't jump and volts don't drop AS bad.

I can still get the 42, every time, if I have the headlights on. But the code 18 hasn't displayed for a while, about the time I cleaned all the grounds (I think).
So, I am definitely going to try to find a connector or harness and probably snag a set of used coils for the fun of it.
The Saga continues.
Your 2 cents is more than welcome. Thanks