This says the intake manifold is malfunctioning. Is it true the '98 has two valve covers, an upper and lower one, and it sticks open due to carbon buildup? In anyone's experience is it cleanable? Or do I have another problem and this diagnosis is wrong? thanks for any and all feedback.

 

The problem was the openings use 2 steel rods connected by a plastic hinge which in my case left the driver side wide open, hence the check engine light plus a rough idle. Used a manual vacuum to find the problem. the hinge costs $7.15 at the ford dealer so both sides were changed to avoid this problem in the near future. Took a lot of time getting to the intake manifold and a contortionist of sorts to do the work. this was on a '98 f150 4.2L v6.

 

Glad you got it fixed. Thanks for the update. That's good information.

 

those hinges are made of plastic and they have four stubs protruding from a round base. two of those stubs broke thus not able to grab the steel rods properly to open and close them. sorry for being vague in the last thread.