i have a 99 dodge ram 1500 5.9 /360. sometimes i start it up and it idles really low like 200rpm-400rpm then it will cut off. other times i will start it and it will idle like 1000rpm-1400rpm. this is all in park other times i can put it in gear and start going and it will idle up and crusie for a little bit then idle down to where it is supposed to. and thats in all gears. another time it was in park and and just started going from 800rpm to 2000 and jumping up and down for about thirty seconds then it quit. would like for some help or suggestions on what this might be. thanks !!

 

IAC valve or camshaft position sensor. if your check engine light isn't on then it isn't the cam position sensor. remove the IAC and clean it then put it back in and see if that fixes it. i was reading somewhere that you can check it by pulling it and starting the truck to see if the pintile moves in and out or to see if its stuck. if you do clean it then don't push on or twist the pintile or you will break it and have to replace it for sure (40$)

 

what is an IAC and where is it located.

 

Intake Air Control valve, it's on the back of the throttle body.

 

And here is a DIY on cleaning the TB and all it's components. https://dodgeforum.com/forum/2nd-gen...ttle-body.html