first of all hello to all! i have a 1990 f150 4x4 with the 4.9 i6 which has 146,000 on it. the motor runs awesome and has plenty of power for only being a six, my problem is the idle on it. i can start it up either cold or hot and it idles 1600-1800 rpms at all times, it doesn't go higher or lower on idle. i've replaced iac, ect, replaced throttle body gasket, cleaned throttle body, everything on the throttle works fine so its not sticking open worked all day looking for vacuum leaks and nothing. its not showing any codes. what else could it be? any suggestions would be very appreciated

mike

 

Throttle position sensor?

 

i've replaced the ect, iac, tps and checked for vacuum leaks and still idles at 1500-1800 rpm replaced throttle body gasket as well and cleaned it up really well

 

When u first start it up let it run for 5-8 seconds then push the throttle so it goes a little high than it is at and see if that helps. Works for me when its on high idle. Kinda like a carb.

 

yeah i tried that and it didn't help at all. seems the warmer the motor goes the higher the rpm. i started it up tonight and it idle anywhere from 15-1800 rpm, and i went inside the house came back out and it was at 2000. a buddy of mine came over and we checked my timing and its at 10, and we bumped it way down and the lowest we could get the rpm at idle was 1100 and it ran like crapso then we bumped it back up to 10 and reconnected the plug the only thing i haven't replaced is the map sensor, or maybe it just has a bad throttle body?