Need some help here. 88 trooper 2.6 After a long run i am having some troubles. The trooper sputs and bucks and I can't figure why. its a daily driver i go about 30 miles round trip to work(30 minutes+/-) and don't have any problems. i went for over an hour the other day and had all sorts of issues. It would totally drop off nearly stalled on the highway.So i got on the back-roads and it did much better at lower speed. i tried feathering the gas to see if i could find a 'happy place' but that didn't work. This happened last year when I went from SC to VA. i replaced fuel filter, regulator and fuse relay. And it solved the problem, looking back its more likely that I haven't gone on long runs since then so i probably replaced all that for naught. Any thoughts?

The first place to start on a 2.6 is to run a compression test. Hopefully it will show everything is OK in that department, but at least you will know.

Jim is very correct. Put a compression gauge on it and start there. After that, if everything was good, I would replace every piece of vacuum hose you can get to.

Beyond that, I would also consider a valve and timing adjustment along with the other tune-up things like maybe an O2 sensor.

The thermal idle control valve under the intake on the right side of the engine might also be suspect if it is leaking or sticking a bit.

Good luck,
Michael