Truck starts to have ruff idle then dies after idle drops considerably.WHat could it be??

sounds like youmight have a TPS or IACV issue, if you have your own scanner, with key on engine off view the data of the vehicle, look at your TPS it should measure between 0% and 100% that will signify a good sensor. also you could have a bad vaccum line on the throttle body, theres two or 3 that i remember, more importantly theres a large rubber one that goes into a small set of solid plastic ones, on my old ram that line rotted out and that, coupled with a bad IACV wouldmake my idle jump up and down and on hot days the truck would have an issue idling

thanks..i have checked the vacuum hoses & done a vacuum test..has good vacuum most of time..and sometimes is loses vacuum.but then goes right back up..i have a mac task master so i will look at tps but i usually cover my basics..i appreciate the reply i may have missed something obvious.with all this snow i have been running around fixing & gettin everything ready.

have you checked your crank shaft sensor? I had the same problem with my truck. I replaced the crank shaft sensor and the world started spinning correctly again.

It also would NOT hurt at all to put a can of sea foam in your gas tank the next time you fill up.