rough idle..sometimes

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Jan 5, 2008 | 11:28 PM

'72f250

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rough idle..sometimes

my father has a 1992 F-150 XLT. it has a 4.9/auto. recently we installed a Jasper remanufactured motor in it. The truck has about a 1000 miles on the new engine and sometimes it idles rough. sometimes its violently rough, somtimes its gentle, sometimes it runs as smooth as a new lincoln. we couldnt figure it out so we took it to our local ford dealership and had our usual mechanic take a look at it. keep in mind, this man has 35 years experience and is an expert at electrical problems. He replaced, the O2 sensor, TFI module, distributor, coil, and Processor. The truck has new plugs, wires, cap, and rotor. nothing has fixed the problem. The fuel injectors tested fine. The only other thing that he thinks could be wrong is maybe a valve isn't seating. A friend of ours said we may have a broken valve spring....any ideas?

Jan 7, 2008 | 08:14 PM

'72f250

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anybody have any idea?

Jan 8, 2008 | 06:03 AM

old hog hauler

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Are you having the same problem as I had.Surge at idle.Read this.

https://www.ford-trucks.com/forums/6...e-surging.html

The end result is That I put on the kit that frank said to try after everything checked out.Wow did that work! You can rest your coffee on the engine now.To start I would by a vacuum gauge,they are cheap and check your vacuum at an idle.If everything checks out dont be scared to put this kit on.It does apply to 6 cyl. as well.Anything with an IAC. Post back with your results.

https://www.ford-trucks.com/forums/6...must-read.html