If i drive at a constant speed for a while and then excelrate its like no throtle,if i down shift it works fine. also noticed at a stop it dosent have the rpm jump up and then settle back down when i push the clutch in.

 

Sounds like you may have low fuel pressure. Possibly an overflow valve or the lift pump is starting to fail. It would be helpful if you could get a fuel pressure reading and a boost pressure reading. Also what are the specs on your truck?

 

Its a2002 . I will take it to the dealer .I put addtive in before when it did this and it worked but not so good this time.thanks for advice.

 

sounds like an APPS problem... check the tech facts for the reset procedure.

 

Mine did the same thing and it was a crankshaft position sensor

 

the dealer replaced the injection pump today. they said it was fixed.Iwill know tomorrow because it would run strange when cold or warm or not for .5 hour.It still could be the crank shaft position sensor. but i hope not thanks for the help.