What's its function?
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What's its function?
I have an 84 F250 W/460 auto trans. In line with the PCV there is a component referred to as "hot idle compensator and tee assembly (p# 9E890). When I am at operating temp, It opens up and lets more air in to the carb via the connecting hose, dropping my rpms. I had no problems w/it until I changed the PCV and cleaned the hot idle compensator up. It was filthy! Can anyone tell me what is it for and why is it doing that? This is my first post as I am a new member.
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From: Virginia
When the underhood temps get very hot, the fuel has a tendency to want to boil in the carb. When it boils, it percolates with bubbles like a coffee maker, and will push fuel out of the carb over into the engine, making it idle rich and run rough. The idle compensator opens up when it gets hot, letting air into the vacuum line, basically a vacuum leak. This makes the engine idle faster, which turns the fan faster, which helps cool down the underhood temps and basically makes it idle better on a very hot day.
It should run faster when the idle compensator is on, not slower.
It should run faster when the idle compensator is on, not slower.
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What's its function?
Franklin2,
Thank you for the info. Unfortunately, the engine does run slower and at times almost shuts off if I don't rev it. Since it is supposed to make the rpm's higher, what could be causing the drop in rpms when it opens?
Thank you for the info. Unfortunately, the engine does run slower and at times almost shuts off if I don't rev it. Since it is supposed to make the rpm's higher, what could be causing the drop in rpms when it opens?
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From: Virginia
The idle screws set too lean or a vacuum leak I suspect. If you pull off a manifold vacuum line anywhere on the engine, the engine will usually run faster unless the idle screws are too far in, or you already have a vacuum leak somewhere, and the extra leak makes it run even leaner.
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