Wondering what was next to replace?
The check engine light has come back on to greet me each drive. The most recent change was the PCV valve, and for a very short time, the truck ran like new. I reset the codes. Still check engine.
Symptoms are: less power. big variations in engine rpm when cresting a hill - you know, when you're into the gas pedal, then you crest the hill, and during the process of letting off on the gas as you cruise the downside of a good steep one, the engine idle will seem to adjust incorrectly often (higher rpm, lower rpm, higher rpm, lower rpm - but very quick adjustments). These symptoms appear very distinctly at a low speed... with little to no gas applied, it almost seems as tho the engine can't make up it's mind.
This truck is approaching 80,000 miles and I'm on the verge of a new suspension, fan belt, and other things - but I want to do as much as possible myself. I'd love to hear from others working a mid-90's 302 truck with comparable miles to know what's in my future to replace next...
Can supply minute details (and bestow many thanks) to any that have time to answer.
spud

 

I had a similar problem with my '93 5.0. I cleaned the idle bypass valve that is attached to the side if the throttle body. It was full of carbon and was not closing properly. while I was at it I also sprayed carb cleaner on the throttle plates and intake to clean them. They were not bad at all. I still get a slight miss when climbing hills but not any where near as bad as before. I also checked my timing and found it ws off. My egr valve was not working either and it was caused by the little solinoid up by the ign. coil being dirty. Just follow the vacuum hose back to it and take it off, carefully take the top off and the bottom too. There is a filter in the top and a small rubber coated disk and a spring in the bottom. My filter was plugged and the disk had some crud stuck to it causing it to not close properly thus causing the egr to act up giving me a code that said " egr not opening" All is well now in that dept. Hope this is of some use to you. SR

 

I didn't see where you retrieved any codes from the computer. I would do this first.

 

Have you tested for a vacuum leak at the upper intake manifold gasket? A leak there can cause those symptoms and can also cause a lot of oil to be pushed throught the crankase ventilation system to your aircase (is the little PCV paper filter in the aircase really oily?).

I had a upper intake manifold gasket leak on my 1990 F250 5.0L. Easy to replace (you need a torx bit and a long extender for the one middle bolt). I had symptoms you described and narrowed it down to the vacuum leak and that fixed things right up. I just wish I'd replaced my valve cover gaskets while I had the upper manifold off since I've got a little oil leaking past them.


Dylan

1990 F250 4x4 5.0L