Hi all:
First time on here. Looks like you have some good stuff here.
My question is for a buddy at work. He has a 1990 F150 4.9L 300.
The problem he has is a mis during normal driving. Not under load
per-say, just cruising around between 30mph-55mph. Usually in
4th gear or overdrive. He has tried alot of things to no avail.
(plugs, wires, fuel filter, added injector cleaner to fuel.) He said he had two codes come up, PIP sensor code 27 and throttle body sensor code 23. He changed the ignition coil and the throttle body sensor. Any Ideas? Doesn't have a problem when going thru the gears. Just when goinig a steady speed. Thank you for
your help in advance.

 

You might check the EGR valve. My 83 f-150 with the 302 did that. I replaced the EGR valve and it ran fine again. Or it could be just a vacuum leak somewhere. Check all the vacuum lines.