Ok its a 1990 k3500 4x4 7.4L automatic with 68k on it. This truck when it first starts up will idle very high and then after about 5 minutes of sitting there it will drop down to normal. Then i take off down the road and about five minutes of driving it starts to spit and sputter for about 2 minutes then it clears up and its fine for the rest of the drive. That only happens maybe 1 out of every 3 times driving it. when i come to a stoplight or I put it in neutral or park after driving it, it is now at a high idle again. Im not sure if its a TPS issue or IAC, or a MAP? I have no clue and would like to know if anybody has an idea? Thank you

 

I would pull the throttle body and give it a good cleaning and replace the gasket between it and the intake. While it is off remove the IAC and clean the tip of it and of course where it screws in. Then check all your vacuum lines and fittings. I just replaced about all of them on my 92 and cleaned the TB - it was relatively cheap and made a world of difference. It used to idle at about 1000 rpm AFTER it was warmed up now it idles around 600 and is smooth as glass. The TBI's are pretty simple creatures and most issues with idling and sputtering usually can be resolved with a good throttle body cleaning and vacuum line check. Also check that the EGR isn't hung up with carbon.

 

I have pulled the throttle body and cleaned it extensivly except i did not pull the IAC, i have replaced each of those gaskets on there also. Ill try cleaning the IAC

 

Man it would have been MUCH easier to clean the area where the IAC screws into with the TB off. It can be done still but your going to wash all that carbon right down into the motor. Mine was absolutely full.

 

Ill take it off before i do that then