Shaking at idle

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May 6, 2016 | 02:43 PM

Cmbyrd

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Shaking at idle

Just bought 1978 F100. Been changing plugs, cap, wires, fuel filter trying to get it running better. Adjusted carb so it would run better. Now it shakes at idle. Any ideas what to look at next?

May 6, 2016 | 02:49 PM

77&79F250

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From: S/W Missouri, Polk county

Ck your spark plugs wiring for being correct and sounds like the carb adjustment might be off.

May 6, 2016 | 03:25 PM

HIO Silver

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Joined: Dec 2009

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From: NorCal

What "shakes"? Do you mean the engine seems is misfire and shakes with an uneven frequency?

Does the engine surge?

May 6, 2016 | 03:45 PM

Cmbyrd

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Engine shakes when at idle. Then it will run smooth for a few seconds. Then start to shake again. So I guess that would be considered surging. I feel stupid asking simple questions. But I always wanted an old truck, just never done much mechanic work.

Quote:

Originally Posted by HIO Silver

What "shakes"? Do you mean the engine seems is misfire and shakes with an uneven frequency?

Does the engine surge?

May 6, 2016 | 04:17 PM

Cmbyrd

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Checked the wiring and it's correct. Backed out adjustment on carb and it's running much better. Thanks.

Quote:

Originally Posted by 77&79F250

Ck your spark plugs wiring for being correct and sounds like the carb adjustment might be off.

May 6, 2016 | 09:47 PM

hasteranger

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Joined: Mar 2010

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From: West Virginia

What did you adjust? Mine does that sometimes.

May 6, 2016 | 09:50 PM

Cmbyrd

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I backed the carb adjustment screws out 1/2 turns each.

Quote:

Originally Posted by hasteranger

What did you adjust? Mine does that sometimes.

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May 6, 2016 | 10:46 PM

orangeford

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Joined: Aug 2000

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From: Eastern, Idaho

In order to correctly setup your carb, get a vacuum gauge and hook up to a manifold vacuum source. Adjust idle screws until max vacuum is achieved and try to adjust each side evenly. To start out you can turn them all the way in and back out about 2 1/2 to 3 turns and then go from there with the gauge. When you find highest vacuum turn the screws back in until it drops and then back out to highest vacuum.

It will run best there.