Rough Idle.. 1992 F150 2WD SUPERCAB

1992 FORD F-150
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JRJOBLIN
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I have a 1992 supercab F-150 2wd with a 5.0 motor. The motor has around 20000 miles on a new rebuild. My problem is rough idle. The car runs ok at 2000 rpm or so, but will not idle. No check engine light, no fault codes. I noticed some green smoky buildup on the motor below the exhaust manifold (by the smog pump.) I tried changing the fuel filter and air filter; no change. I also upped the idle set screw a good bit, but it still wont idle below 1500rpm's or so.

Any advice u guys can give me is greatly appreciated.
:D
John

-ps, the truck is at around 140000 miles on the speedo.
Feb 23, 2007 at 7:54 PM
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KIN CHAN
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chk vacuum leaks !!!!!!!
Feb 24, 2007 at 7:09 AM
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STRAILER
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If no vacuum remove spark plugs to check compression, all the cylinders should be close to the same, you might have a leaking intake valve.
Feb 24, 2007 at 11:54 AM
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JRJOBLIN
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So far:
New motor mounts, Right exhaust manifold, Rotor, Cap, Plugs, Wires, PCV valve.... Still no change. When I pulled the plugs they were all moist with gas. All plugs looked identical to one another, there were not any diffrences in buildup or color between them.

With no check engine light can I have a bad oxygen/fuel mixture? Could I have slipped time a notch on the timing belt? Any additional advice is truly appreciated.

John
Mar 9, 2007 at 11:40 AM