Engine floundering off-idle...

Well lately my '88 4.0 auto has been acting up by taking a while cranking over to start (30 - 60 sec) but only after driving for an extended period and not every time...Last night driving home from work and after 20 minutes highway driving with no problems starting or accelerating, I got off at my exit, was waiting at bottom of off-ramp, light changed and it started completely stumbling, and popping with any gas given. The only way I was able to get it home was by placing in drive and letting it idle home (that took a while). Could the fresh tank of gas I filled last night at a station I rarely use cause this? It was also pretty wet out here in Chicago last night...Could something have gotten wet? If it is a fuel delivery issue why would it be ok for a few minutes street driving,then highway, then go to sh** post highway?
Just wondering if anyone has had this happen or has any guesses, or suggestions. Any would be greatly appreciated

Gil

I had a 2.8 S-10 that did that going down the interstate at 80mph, started bucking and missing, no power or acceleration, I ended up taking the next off ramp 3 miles later on and pulled into a gas station. Shut it off, was told a 3 hour wait to look at it so I fired it backup, played with the gas pedel for a couple of minutes and it seemed fine, the problem never came back. To this day no idea what caused it.
If you just filled up you could have gotten water in there, stick in a can of dry gas and see what happens, can't hurt. Some sloppy bulk delivery drivers have been known to not close the tank caps completely or allow water into the bulk tank or you might have been one of the lucky ones who filled up minutes after a delivery when all the crud is stirred up, not all gasoline pump filters are created or maintained equally. Hopefully your fuel filter caught any crud before it could reach the injectors. Could also be a vacum leak, what kind of shape are your vac lines, if original they are over 14 years old. Time for some preventive maintenance maybe