High idle rpms please help!!!

Asked by Aug 04, 2017 at 12:08 AM about the 1996 Ford F-150 XLT 4WD LB

Question type: Maintenance & Repair

my truck idled at 2,000 rpm then after a while it would go down then want to go up
again, i looked online and saw that people normally changed the idle air control
valve so i got a new one, but i still have the same problem,i played with the idle
screw and got it down to about 1,100 rpm. I unplugged the IAC  and the truck runs
great low idles rpms and everything, i took it for a test drive (plugged the IAC back
in) and when i push the clutch and hold it there the rpm went up it hit 3,000. also
when i let go of the gas pedal the rpms are still up and the truck goes by itself.  
Could my problem be the throttle positioning  sensor, also i checked and there
doesn't seem to be any vacuum hoes leaks.

Been looking for possible solutions for hours but got nothing i would really  
appreciate  it if someone could help me.

2 Answers


it would be hard to diagnose without seeing the actual car, first thing to check is if there a "check engine" light, that might give you a code that makes it a lot easier to check, check the throttle body if its dirty but it could be many different things, its best to have a mechanic look at it instead of just wasting money on part trying to guess the problem

no there wasn't any check engine light before i replaced the IAC, i will probably have to end up taking it to a mechanic whenever i can afford it, I appreciate you taking a look at my question tho

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