I have 1991 f-150 with a 302. My problem is this; the idle started to get erratic about a week ago, from almost stalling at 200 rpm back up to about 800 or so rather rapidly. Currently the truck will not even idle under it's own power you have run it at 2000 or above for it even stay running. Working for a parts store I have the ability to throw whatever at it I want and the list goes like this: IAC, TPS, TEMP. SENSOR, MAP, EGR POSITION SENSOR, EGR VACUUM SOLENOID, EGR. I just replaced the upper intake gaskets and have 3 throttle bodies that I have switched around just in case. I originally thought sensor because the problem was so instant, but as it gets worse and worse it seems more mechanical. Anybody have any ideas? Actually as I write this i'm thinking I should check fuel pressure.

 

Stop throwing parts at it and check for codes.

 

Yep, sounds like it's time to pull the pitcher & pull some error codes. Work in a parts store? http://www.handsontools.com/Equus-In...ol_p_5574.html Fuel pressure check wouldn't hurt either.

 

This scanner can retrieve codes without a CEL?

 

It has digital numeric display. It don need no stinkin "CEL"!!! Fuel & Vac pressures would also help. Even, dare I suggest............Dry &wet compression test!