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Old 12-14-2004, 12:00 PM
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vibrating ford POS

Hey guys, Iv'e got a kinda wierd problem. 1990 F150, 5.0L, recent tune up, and this thing has a serious engine vibration, especially after it shifts into third gear. Almost feels like your driving over washboard. Timing is set to aftory 10*, spout disconnected. Plugs are good color, new wires, cap, rotor. Compression okay. You put it to the floor, get the revs up, it goes away, comes back when the revs go down. I'm just runnung out of places to look, any ideas?

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Old 12-14-2004, 12:12 PM
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Sounds like weak spark to one of the cylinders, place a timing light on each plug wire one at a time to find the one with the problem. Could be a mixed up plug wire too, check your firing order.
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Old 12-14-2004, 12:16 PM
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Firing order is good, checked that first off. New wires, cap, rotor, but is possible I have a bad plug somewhere. Will do the timing light check, and see what I find. Thanks.
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Old 12-14-2004, 12:17 PM
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vibration

does it do it when the vehicle is not moving? - if not then it will be a drivetrain problem, most likely a driveshaft universal joint and/or transmission mount.
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Old 12-14-2004, 12:42 PM
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Lock up converter taking a dump? Lockup solonoid malfunctioning?
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Old 12-14-2004, 01:54 PM
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Does it when stationary, I kinda wondered about lockup.
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Old 12-14-2004, 03:37 PM
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Try disconnecting all the drive belts then try to get it to vibrate when stationary. Could be a fan clutch, tensioner pulleys, etc.
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Old 12-14-2004, 05:06 PM
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Harmonic balancer going south?
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Old 12-14-2004, 05:17 PM
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When you say stationary,you mean in Neutral or Park and not in gear correct?
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Old 12-14-2004, 10:51 PM
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I found it!! Lost most of # 8 intake lobe. The valve is opening, but not nearly enough. After seeing some of the posts, I decided to re-do the compression test, as I had someone else do it for me 'cause I was busy on another vehical. Turns out #8 was low, and wet test didn't bring it up. Pulled the cover off, intake on 8 moved about half as much as the rest. Looks like cam swap time!! Thaks for all the quick replys, guys.
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