94 Ford F150 IAC issue

[john.wells]

351 engine: From cold start, truck goes into high idle as it should, but immediately drops off to low idle after anywhere from around 5 to 30 seconds and will die if driven unless it has warmed up. Recently replaced TPS. Any correlation? I have disconnected battery a couple of times and tried letting idle after for the recommended 15 minutes for the KAM to re-learn, but same result. Would this be an ECM issue, or could the IAC just be not functioning correctly (either full-on, or full-off)?

[Big Buck Buster]

Have you checked the throttle opening for coaking? If it is dirty, clean it with carb clean. I have seen many of them coak up the small holes in the "butterflys".

[Jeremy airjer W]

Did you pull of the throttle body to change the TPS?

[Scott K]

Did this problem start after the TP replacement? If so ck the output voltage of the tp at idle, it should be between .5-1.1 volts, then open the throttle and the voltage should increase as you open the throttle. If the voltage is ok, remove the idle control valve and clean it, and retest. If it still doesnt idle, check vacuum leaks, if none are found, adjust base idle.

[fishing tech]

Upper intake gasket?