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Discussion Starter · #1 ·
On my last trip out of town I had this intermittent situation happened three times. After stopping the car and shifting the trans into Park the engine would rev up to 2500, one time as high as 3000 RPM. I'd shut the engine off and it would restart and idle normally. It was quite hot here last week, and it has never done this before. I have to go out of town again next week, so I'll find out if it does it again, but what might cause this kind of situation?
 

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I had something similar happen to me in a '87 Ranger. It ended up being the MAP sensor was bad. It took forever to figure it out because the sensor wasn't bad enough to throw any codes. It was bad enough to trick the engine into thinking it was on top of Mt Everest though and that is what caused the random high idle. Might also want to check out your idle air control valve to be sure that it isn't sticking.
 

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Discussion Starter · #3 ·
I had something similar happen to me in a '87 Ranger. It ended up being the MAP sensor was bad. It took forever to figure it out because the sensor wasn't bad enough to throw any codes. It was bad enough to trick the engine into thinking it was on top of Mt Everest though and that is what caused the random high idle. Might also want to check out your idle air control valve to be sure that it isn't sticking.
Thanks. Might have to get the codes checked.
 

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Make sure nothing is causing your throttle to hang up like a binding cable or??

Otherwise bad TPS or sticking IAC are the 2 most likely causes. If you can get it to act up then try tapping on the IAC, if the idle immediately drops then the IAC is likely sticking.
 
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