Kinda weird idle issue

[xtrempickup]

Truck runs well, but sometimes sitting at a stop idleing it will puff a little and seem to jump or the idle will fluctuate up a bit with my foot on the brake. Any ideas?

[Plowboy81]

Straight or auto. If its an auto could be the auto lock switch on the trans going back. The switch that works the clutch in the trans on an auto.

[xtrempickup]

yes its an automatic. it only does it when its sitting in drive at a stop for a couple minutes it just feels like it wants to go, it wont do it in neutral or when driving

[Plowboy81]

Sounds like it is that switch on the trans going bad. When that switch goes bad it well do that and sometimes it will kill the truck. I have seen it idal the truck up and not idal it down. It will work fine when you are driving it. That switch only works when the transmission is shifting down and into what we call nutural. Which is like when you are holding the clutch in on a stright. It tells the engine to idel down cause the trans clutch is in. Cant remember the name for it. Thank its called Torque Converter Lock switch or Transmission Solenoid. If you put it on a computer it well tell you exactly which switch to replace.

[xtrempickup]

sounds good thanks