My 87 Ford F150, 300 str 6 will start and idle just dandy on a cold start.. After warmed up, I turn it off, restart, and the idle varies from 1500 down to 500 for about 20 seconds, then is fine. I was told it was the map sensor. I replced it, and it still does it. And today, after settling into it's normal idle, I pulled out and about 100 feet later it just plain stopped running. After sitting for about 15 minutes, it fired right up and ran fine. ANY IDEAS????
Check the throttle body for crud in the body and the plate, clean it if dirty, then remove the IAC valve and clean it, then reinstall, disconnect the battery negative terminal, turn on the headlights and wait 30 seconds, turn off the headlights, reconnect the battery, start engine and drive as you normally do, this will relearn the computer, this is an old Ford OBD 1system so if it causes any thing further you may have to find a shop that can run a diagnostic on it. You migh consider replacing the fuel filter, if it is partially plugged on that engine you might not get enough flow through the fuel rail to prevent vapor lock.
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