Truck Sputters and Cuts Back in 10th Gear?

[Hawkjr]

My POS day cab Volvo is having a serious problem and none of the idiots in the shop can figure what it is.. Going down the road in 9th or 10th the truck starts cutting back, sometimes dropping 5mph then going back up to speed.. No hills or anything, on flat ground it does this.. We changed the fuel filter and its still doing it.. someone suggest it could be the ECU.. Any suggestions??

[firebird_1252]

volvo motor? i used to drive one and it would do the same thing.. no spudder.. it'd slow down 10-15mph on flat ground then pick back up and do it all over again.. dealer found no problems.

[Jackrabbit379]

Fuel pump itself?

[Shnerdly]

I don't know what year your truck is or what engine you have but I was driving an 07 KW with an ISX in it last year. It had a random loss of power and would sometimes smoke like an old Mack when pulling a hill. After we did everything else, we took it to Cummins and they said it was the Variable Geometry Turbo ($1800). I didn't think that could be right but they changed the turbo when it came in two days later and it solved the problem completely.