THis only happens occasionally but it kinda worries me, but when I start my truck the rpm start to jump up then do and it jerks the truck. When I start it, it drops to about 500 then jumps to about 1000-1200 and it sounds like a muscle car with crazy HP when they like rev up and down just idling. But when it does this I give it some gas and rev it up and it seems to go away. It has no effect on my driving. Only at idle Speed. Anyone think they know what it could be??

 

??

 

Do a serch for IAC (Idle Air Control)... probably needs cleaned or replaced... This is where I would start...