Bigred4x4I6

Ok so i just bought this 1989 ford f250 with the 5.0 and it has a very high idle speed...so here is what it does....i can start it up and it runs normal as soon as i put the truck in gear and hit the gas the idle flys up to abou 2.5 grand...the only way i can get it to stop is buy pulling over and unpluging the idle air speed sensor...the thing is ive replaced the sensor already and it still does the same thing......my ? is my temp sensor i think is shot because my temp gauge does not come up so if the temp sensor is out would this cause my idle to be so high?? i dnt think its a vacume line because it runs fine when the idle air sensor is unpluged...so somthings telling the senor to give the truck a high idle but what? thanks

partsforstangs

One quick thing to try. disconnect the battery for at least 30 minutes. This may help clear any codes that bad sensor you swapped out was giving. This may clear that idle issue. Hey its worth a try and cost nothing look closely at your throttle body and make sure its closing completely and not getting hung up.

Best of luck.