[96dieselfan]

I have a 1996 F250 Turbo diesel, 7.3L, manual trans. It runs well cold, but after heating up say on the highway, when I decelerate, like going down off ramp, it idles rough and acts like it wants to stall, but doesn't. It will do this rough idle for about 10 secs, then smooths out. It has about 2,000 miles on Rotella T 15-40 oil, but the oil was last changed about a year ago. Don't drive her much. It has about 75,000 miles on her. What gives?

 

[Evel486]

Possibly your oil is foaming. Is the level ok?
Try holding the rpm at 3500 in neutral for 2 minutes, then back off the throttle quickly. If the engine then idles rough you have a high pressure oil issue. If the level is ok, remove the IPR valve and clean it.

 

[96dieselfan]

Thanks for the help! I pulled the dipstick a little bit ago, after the truck sat all night, and it looks like the oil is about a quart too much. About an eighth above full on the dipstick. The quality looked good, clear, not black or too discolored. I guess it could be too high pressure! Why would Rotella T foam, I think it is the recommended oil, but as I said, it's been there for a year, but only about 2,000 miles. Thanks!