1986 Isuzu Trooper Trooper jerks along

Rasmataz, thanks for the feedback. This is a carbureted model--no fuel injector, so it looks like your first few possibilities are not possible. Any best guesses for one w/ a carbureter? I will say that the *only* thing i've ever experienced at all like this was the fuel pump failing, which caused a similar type of jerking movement. But it was replaced four years ago and there have been *no* similar problems since. At the time, the mechanic (an older, very experienced guy) suggested there could be rust(?) Flakes breaking off inside the tank and intermittently plugging the fuel line intake, but this was never checked. How's that for a stretch?

Well, I was mistaken about the wire. I just took it over to a place called Import Auto Clinic here in Madison, and the owner took it around the block. With engine running, he then started removing plug wires from the distributor one at a time and noticed that nothing changed when he removed the #2 wire. He knew after driving it for 30 seconds exactly what was wrong. (In fact, I think he even somehow knew it was the #2 cylinder before doing anything). He showed that he could pluck the wire right off the plug, but the connector remained on the plug, i.E. The wire was history! He re-crimped it, reattached it to the plug, and the vehicle runs like new.

Hey, i'm a geologist, not a mechanic.

Just meant to add that it's incredible to me that a dead spark plug wire could cause such jerking while driving. I mean, I would have thought (as a geologist) that the other three cylinders would supply enough power to cruise along more or less normally, even with one cylinder not firing, but that's obviously not the case.