I have a 93 F150 5.0 EFI supercab w/AOD. It's got almost 200,000 miles on it and it runs great, except.....

...when I lift off the throttle after accelerating or even cruising at speed, the engine revs down, just like a manual downshifting, and it's just as loud as when I'm accelerating. I can actually feel the truck losing power when it does this. Is this just a timing problem or is blowback from the exhaust? There are no leaks in the exhaust that I can find.:-fire

 

Do you use alot of oil? I would perform a compression check on a motor with that many miles.

 

It uses almost no oil and there is a lgood compression in the cylinders... any other ideas.

 

Maybe a new PCV would help? Just a guess. Is the compression within 20% of each other?

 

definitly check your pcv valve and the hose to the valve..also is there alot of oil in the filter box. there is a small filter in the box you might wanna check that one to..i have an 87 f150 with almost 300k on it. its all org (eng an trans ) it has a small amount of blow by into the air filter box. about every 10k i have to replace that small filter ..no biggy, truck runs like achamp !

 

I was not aware that the PCV would cause that "downshifting" in an automatic transmission.... I'll give it a shot.