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Thanks, Thor, but I looked everywhere and cannot find any such requirement for the I6 LR2, in the manual nor elsewhere. Perhaps you saw it for the later engines? The factory manual only tells you to swap in a new MAP sensor, nothing else in its 1400 plus pages. But I'd be very interested in seeing the source your research found, though, if you have it handy. Meanwhile, the problem is fixed and the engine runs fine with the new MAP sensor... see update in next post.
OK and Eureka, I found the problem: I remembered that some past mechanic had noticed, or been the one who broke it, that the connector lock was broken off. So he/she put a glob of silicone on the clip to hold it in place. So I thought that maybe a bit of that old "rubber" was blocking the connector from going in all the way, even though it felt as though it was... and was bottoming out.
So I took the MAP sensor out, and played with the connector. I did find old rubber in there, and cleaned it out. I could push the connector all the way on, but then it would push back a small amount! I studied it carefully, and it turned out that the original rubber seal... you know the ones, ribbed seals that are to keep water out of the connector... was slightly torn, and deformed. So when I thought the connector was going on, it was just bunching up this bad seal, and the connector was not going on all the way. This was hard to see, because when you put this connector on, you normally cannot see how far it is on... that view is blocked. But when out in my hands, I could easily see it.
The seal was too far gone, so I pulled it out. Then I pushed the connector all the way on, and sealed just the gap with silicone. To keep the connector in place, I looped a tie-wrap around the sensor and the connector and pulled it tight.
The car works fine now... no lope, no stutter, and does not throw any MAP error code. Thank heaven for stupid little problems like this... Re-wiring a new connector on there would have been a bear.
Thanks, Thor! I'll read through those tonight, and report back... we have a rare mid-40's degree f. day here, and I'm trying to catch up on all the stuff outside before the temps plummet again.... like tomorrow! If I do have to still have this programming done, at least the truck will be back together and working. All the best, Rich.
VERY tiny gremlins. The distance the connection was held out was somewhere less than 1/8". The contacts were close enough to be touching at times, I think, explaining the intermittent nature of this. Or the gremlins were wearing tin foil and dancing.
FYI, here is a (blurry) pic looking up at the sensor and wiring connector after I tie-wrapped it. Jury rig no doubt, but it is not coming apart until the tie wrap is clipped. It neatly fit around both parts, and the sensor even has a little "horn" on a corner, which keeps the tie wrap in place. The sensor sits above it's mounting grommet by about 3/16", so there is plenty of room for the thickness of the tie wrap on the other side.
In the picture, the sensor is hanging about 6 inches below the place in the manifold that it inserts into. Luckily this is one sensor that you can remove and replace under the car, even though you can't see all of it and have to do it by feel (why I didn't see the little space the connector had, until I took it out and could see it).
One BTW: For anyone reading this, doing their throttle body, you CAN do it from under the car, usually. I could not, because the end of one of the four mounting screws (they protrude a bit beyond the hole in the plastic mounting flange) was rusty. I could not turn it easily through the plastic, and so figured I'd ruin the hole in the manifold. I removed the manifold so I could file the end of that screw down, and soak everything with PB Blaster, and take my time. But if the mounting screws are not rusty, you can get in there and remove them. I bit tight, but doable, I think.
I once had a CH-46 in my hangar in the Marines for a month because the VHF radio outgoing audio would not work. We spent weeks and very long nights chasing down the problem. I was about to order an entire harness, not a small thing, would take a very long time to replace correctly, when one of my techs came in and said he fixed it. One. Tiny. Fricking. Pin. Socket. It had opened up just a tiny fraction of an inch too much over time, and the male pin on the radio connector would not make contact. 10 minute fix. Earned himself a very long weekend.
