i am working on a 1999 kenworth concrete truck with an ism cummins in it. It was running fine up until yesterday, now throttle will not work all the time. The truck will start and idle fine, most of the time throttle works like it should, however sometime it will not do anything, when this happens it will not go above an idle, let off accelerator and try again after 30 or 45 seconds and it will work fine. i am thinking tps sensor at peddle or the peddle assembly itself but trying to narrow it down before throwing parts at it. I am by no means a mechanic, supposed to be assistant manage but they failed to tell me that also means mechanic/maintenance guy. any help would be appreciate before i put the truck in the shop. thanks.