Lose power in 4th

[velotuntshiz]

I recently bought a HDJ81 1991 turbo diesel cruiser. I took it on its first back country fly fishing trip and all was well until I started to lose power in 4th gear. It was very hot outside and I seemed to lose turbo boost. It is an automatic truck. Took it fo another spin through the city and onto the highway. It seems as though the turbo is fine as the truck works through gears 1-3. It also seems like the turbo engages in 4th, but there is no power to be had. I get stuck cruising very slowly. Earlier today on a hilly highway it struggled to hit 90 km/hr. On flat sections 100km was top speed. On other highway trips it has chugged along nicely at 100 and had some power at 100 to accelerate to pass a few cars.

Any thoughts on what may have caused this sudden loss of power?

Thanks in advance!

[Tapage]

This question should go better in the diesel section .. but the turbo it's always spining until something wrong goes of you shutoff your engine ..

The hability of producing boost from a turbo depends on the load, diesel, air and the shape of it .. wear or not.

Anycase ... if your truck drive and perform fine at 1 - 2 - 3 shift .. and fail in OD maybe it's the tranny and not the engine ..

How goes your rpm throught the powerband . ?

[velotuntshiz]

Thanks for the response...and sorry for my delayed reply...we moved and I just set up the computer!

The RPM's seem to be normal through the powerband. I know a mechanic and he suggested the simple solutions first...so, at his request, I changed the gas filter...seemed to make a difference! I have not lost power in 4th on the highway since! Suppose it was a momentary fuel supply issue!?