Idle problem

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Jul 3, 1999 | 07:40 PM

island

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Joined: Jul 1999

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Idle problem

On my 1990 F150 5L (351) the idle will not come down low. I changed the throttle position sensor but it stayed the same. Any help would be appreciated.
Harry

Jul 3, 1999 | 10:17 PM

Mulletwagon

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Joined: Jun 1999

Posts: 349

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Idle problem

Prime suspect in most idle problems is the idle by pass (BYB) valve. It is that dufer on the intake manifold held on by two bolts and connected with three wires or so. Disassemble it and clean it with carb cleaner. Also clean the throttle bore in the viscinity of the throttle plate (what the old guys call the butterfly). Gunk in this area tends to overtask the by pass valve. The more common problem is stalling, however, give it a shot.

Jul 4, 1999 | 04:37 PM

harry

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Joined: Jul 1999

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Idle problem

thanks for the tips on the high idle problem. I did as you suggested, clean the throttle bores and butterfly plates also removed and cleaned with thinner the idle by pass valve plunger. No joy.
I'm going to try spray on carb cleaner in the by pass valve as someone on this BBS suggested as I can still see carbon in there.