extremely high RPM
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Junior User
Joined: May 2008
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From: Cayce/Columbia/Florence
extremely high RPM
hello, my dad recently got a 94 F150 2wd manual transmission with the 4.9L engine in it for free. It wasn't running as it needed freeze plugs. Well he got it and put the freeze plugs in and got everything put back together and when we started it up the motor revved up to what I am guessing is 3000 to 4000 rpm. I searched on here and found vacuum leaks may cause high idle so we went over everything, I even pulled my 93 f150 with a 4.9 beside it to match everything up and then sprayed starting fluid while the engine was running so see if it would increase at all. Nothing. I then took the IAC off and cleaned it even though it was fairly clean to begin with. I can turn the idle down by turning the distributor down but then won't crank back until you turn the distributor back. Where else should I look or what else should I do. I pulled the KOEO codes and only got one. it was a 520 something,(something saying the computer couldn't find neutral or park). Any help will be appreciated.
Thanks,
John
Thanks,
John
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Joined: Apr 2004
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Have you check everything mechanical, from the pedal to the butterfly? A cable that is unraveled inside will hold the throttle open, for example.
And did you check the intake manifold to head gaskets and how it seals?
And did you check the intake manifold to head gaskets and how it seals?
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Joined: May 2008
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From: Cayce/Columbia/Florence
I checked the pedal and everything. the butterfly is staying closed. I took the top of the air box with the hoses off and could see the butterfly staying closed. As far as the head to manifold gasket they are new and I did spray starting fluid around them with no change.
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Joined: Apr 2005
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might know waht's doing
Just did work on my truck and ran into the same problem. Good news is it's an easy fix. Check where your throttle cable was put back. There are 2 spots where the cable can go thru, one is kinda rectangular and the other is round. I originally put in in the rectangular one and it revved very high. I moved it 1.5 inches to the round slot and revs came down.
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