Burnt valve?
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Postmaster
Joined: Feb 2003
Posts: 3,441
Likes: 5
From: Muskegon, MI (home)
Burnt valve?
I picked up a 91 RC SB 4wd F150, it has the 5.0L/5speed. The upper intake plenum had a blown out gasket and a few of the vacuum lines. I pulled the upper plenum and went through all the vacuum lines that needed it. I got it back together and running, it definitely runs better but it still has a misfire under load. I don't know how long it was ran with the bad intake gasket. I suspect I may have a burnt intake valve. Am I on the right track with this? Any thoughts or suggestions? Thanks again!
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Postmaster
Joined: Feb 2003
Posts: 3,441
Likes: 5
From: Muskegon, MI (home)
Sorry I was half asleep when I posted this last night. I put a fresh set of plugs and wires on it, the cap and rotor were in good shape. Other than a very weak battery, it pops off when you hit the key. It idles fairly smooth, when you give it some throttle it hesitates a little bit. Holding the throttle at pretty much any position, stumbles and misses; low on power. I have not checked the injectors yet. I notice a popping/stutter in the exhaust. I don't know much on the history of the truck, I can tell it was neglected pretty badly. From what I know/understand, the symptoms are textbook for a burnt valve. I am not as familiar with the Windsor series, most of my experience is with 460s and 300 sixes
Hotshot
Joined: May 2003
Posts: 11,141
Likes: 25
From: south louisiana
Well the upper intake gasket leaking won't burn a valve. Did you check the ignition timing ? If so, where's it set ? I would also change that cap and rotor, they make look fine but could still be bad, letting the spark jump from one terminal to another. It would also be a good idea to get those injectors cleaned or replaced.
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