Chevy 1/2 ton truck with a 350, 2WD automatic. Driving merrily along and all the dash lights come on, you lose ignition for a split second and then all is well. Split second power loss, even though the check engine light flashed, it wasn't on long enough for the issue to be stored in the OBD1.
If I remove the alternator wire it doesn't happen, I bought a new alternator.
What I've done:
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Disconnect and clean all electrical connectors I could find.
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Put a new gasket under the MAP sensor (it was really dry)
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Checked the MAP sensor IAW the shop manual and it checked out OK.
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Replaced all the dry rotted plastic vacuum lines.
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Replaced the Ignition Control Module.
In over my head so I brought it to a shop. They kept it for a week, couldn't find anything. Since I cleaned the connectors, the momentary flash of no ignition is more pronounced and the truck just fall flat on its face for a second.
I drove it around for the weekend because I had to haul a trailer, damn near didn't make it home. Brought it back to the shop. ~$200 later I still don't have answers.
Because it didn't happen when the alternator is disconnected and a new one didn't fix it, is something back feeding through the system?
Oy. Thoughts?
In reply to trucke:
I came into this thread preparing to share links to a few AMC clubs and collectors myself 
Replace the ignition switch.
My first thought is bad connection or bad wire. Start it up, and wiggle every wire harness in the engine bay until the problem shows up. You're basically playing a game of colder, hotter until you narrow it down to the exact spot.
You better fix this for us.
I liked the movie better than the car.
Also, ignition switch is going bad.
06HHR
HalfDork
11/21/16 2:05 p.m.
If the ignition switch turns out to be ok, have the shop test for a dying pick-up coil in the distributor. That wouldn't throw a code either IIRC. I was looking for a Gremlin too, specifically the one from the hotlinked pictures thread with the early Hemi sitting in the foreground..
OK fine I'll do it because I'm eating a sandwich and my surfing finger is itchy.
I bet he wishes someone was watching...
Or this.
But back to the original question - I second the ignition switch thought. Try wiggling the key while running and see if you can cause the glitch.
Not sure why you guys were all showing drag racers; isn't this a corner carving site? How about this one?
Remember Dennis Shaw? This was about the same time C&D with Pat Bedard was running an RX-2.
daeman
HalfDork
11/21/16 3:42 p.m.
I'll third the ignition switch. The fact that all your Dash lights come on is a fair clue.
If not that, then if there is a primary relay for the ignition, then that may be the problem.
OK, thanks for the help guys.
stan_d
Dork
11/21/16 5:39 p.m.
Do you have a big batch of keys? A lot of weight hanging from the lock ?
44Dwarf
UltraDork
11/21/16 6:05 p.m.
By chance, I had a similar problem in a dodge pickup. It finally got bad enough to pop the ign fuse so I swapped in an auto-reset curcuit breaker. The next night i was on my normal bumpy ride down rt2 and all of a sudden it shut down like 5 times in 200ft...i looked down to find my ash tray on fire.... a nickel was inside the cig light socket.
Do you toss coins in your ash tray?
In reply to 44Dwarf:
I've never heard of that before. Wild
I hear water will cure all gremlins 
In reply to 44Dwarf:
I don't think GM ever did something quite as silly as putting the ignition on the same circuit as the lighter. As I recall my GM car (which also like to attract change to the lighter socket and blow) had the socket on it's own circuit, which also for no reason in particular powered the OBD2 port and the horn.
No big keys, key ring has two keys and a bottle opener.
Ashtray is empty, I use the cigarette lighter hole to plug in the GPS device every once in a while.
