only running on 3cyl.

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Sep 6, 2004 | 01:58 PM

79bronco300-6

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only running on 3cyl.

well i finally got the hood and fenders back on my truck. it sat maybe two weeks tops without running. when i had it running last it ran perfect. now when i fired it up today to go get some gasoline it started running really rough. i poped the hood. and when i pulled any of the first 3 spark plugs it would get worse but if i pulled any of the back three wires it would run just as it was so what would cause it to miss on the back three cyls but not the front three?

Sep 6, 2004 | 05:14 PM

javi2001

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Joined: Apr 2003

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From: Venezuela

I guees you double-check ignition system...

Usually valves get stuck OR...
Some Lifters get oil pressure beffore engine runs, it cause problems if valve springs are weak...

Sep 6, 2004 | 07:21 PM

srercrcr

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I guess I would make sure there is spark being delivered at the three bad plugs.
Check the dist cap too.
Then do a compression check (or hook up a vacuum gauge...any wobble in the needle?)

Sep 8, 2004 | 03:46 PM

79bronco300-6

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got it figured out. the rear float on my edelbrock was stuck keeping fuel from the back half of the motor.

Sep 9, 2004 | 10:46 AM

Sukhoi

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I have sort of the same problem, only it's cylinders 3 and 4 that aren't working.

So far I have done a complete tuneup, and checked that the plugs are firing. A suggestions what I should look for at this point?

Thanks