"Engine Surging When A/C Goes On"

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Jul 1, 2004 | 05:27 PM

IES

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"Engine Surging When A/C Goes On"

Hey everyone,
I just had to replace the Alternator and the battery on my truck. After replacing those parts the engine began to surge(idle would go up and down) when the A/C would be turned on. Engine never did this before. Mechanic rechecked The Alternator and battery with the volt meter and it showed no fluctuating in the voltage.

Is there some kind of sensor that regulates the idle when the A/C goes on?

1990, F150, 302 engine

Last edited by IES; Jul 1, 2004 at 05:30 PM.

Jul 2, 2004 | 06:59 AM

jroehl

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From: Lafayette, IN

My '93 F250 351 was doing the same thing for a short while. It turned out to be a slightly loose vacuum hose, so it was also throwing engine codes.

Hope that helps/works.

Jason

Jul 2, 2004 | 12:20 PM

HardScrabble

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I second the vacuum leak idea. Check the lines that may have gotten in the way while changing the alternator.

There are also vacuum controls in your AC system. Check those also.

Jul 5, 2004 | 09:22 PM

vaughan_psk

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I think your problem could be In the throttle control sencor or I think that`s what its called. it`s below your throttle leaver on EFI two screw`s hold it on.it gets carbin built up in it and causes idle fluctuation you can take it off and clean it with carb cleaner hope this helps cv.

Jul 6, 2004 | 12:09 PM

IES

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Hey everyone,
I took the truck to a mechanic and he adjusted the idle by raising the RPM's by turning a screw that's located by throtle body area. Idle stays steady now when the A/C goes on or off. Now I just have some smoke when I take off but truck is running smooth for having 190,000 miles. I poured a bottle of Techron in it, he says it helps to clean some of the build up on the valves which could be causing the smoke when u take off.

Jul 6, 2004 | 12:33 PM

couleeman

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From: Magrath

Determine if the smoke is from oil, gas or antifreeze. If it is gas, it could be from getting the idle adjusted and burning to rich. He may of masked the problem of the surging instead of fixing it.

Jul 6, 2004 | 04:35 PM

IES

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How can I determine what kind of smoke it is?

And if he did mask the problem, how do I turn that screw he turn back towhat is suppose to be set at?

The truck was idling at 700 RPM's and it would drop to 500 RPM's when the A/C would go on, turning the engine off at idle.

Now it idles more at 800 RPM's and drops down to 6-to700 RPM's(can't tell exactly) and it stays steady.

How do I know if I'm burning rich?

Thanks for all the help!