Hi all,
New member here, I got a 1990 F250 with a 460fi a few years ago with an older airstream. The truck was well cared for and was used to haul Airstreams(both owners) all around the country. I'm a pretty decent mechanic but these symptoms have me scratching my head and I'd love to keep the truck as it has a great body and interior. So...here goes the symptoms:

Major issue is truck shudders and has no power at 1200 - 1500 rpm in drive.
Turning off the AOD helps and driving it in 2nd gear I get no noticeable shake but just having it in park and increasing the RPMs to that range I get a shake.
So...I'm going to check the spark plug wires to make sure they are in the right order, also going to pull the plus and do compression check with a screw-in gauge across all cylinders.

I have noticed that plastic gas fume containers have been eaten by rats and have holes in them....not sure this would cause the issue but they do have vacuum lines going into them so I'll replace them.
Could EGR be the issue?
Now here are some bizarre other symptoms that may or may not be related:
- Engine smokes(sometimes).....It starts up like a champ every time, idles well and no smoke on startup.
- If I let it idle no smoke and oil pressure is good...BUT.....if I put it in Drive(and not move it), the oil pressure dives and if I put it back in park...the pressure stays low and it will smoke like crazy.
- If I drive it after smoking...it will smoke for a while, then clear up fine or smoke just a little. It has good oil pressure over 900 rpm.
The smoke is gray with maybe a slight bit of blue in it. These symptoms are odd and I'm wondering if it could have something to do with the auto transmission, I believe vacuum modulator....do the symptoms sound at all like that could be the issue?

It's had this issue since I've owned it and I hardly drive the truck but am now using it as a work truck on some vacation property I bought so am driving it more and want to get to the bottom of the issue but not sure where to begin(other than plug sequence, leak down testing, new oil sender to make sure the low pressure is not a sender issue) but the odd other symptoms are telling me something else may be going on. Hoping you folks could chime in on similar experiences with these symptoms.. your help is much appreciated. I typically work on older classics that have no smog/manual tranny/carbs so all the hoses, pumps, valves and what they can cause if failing is a bit new to me....I have thought about dropping a crate/carb motor in this thing but that would be a whole other project on top of the 10 I already have going(yes...I am ADD!).
Thanks again for any help...Paul.

 

IMHO, time to do real trouble shooting including diagnostics (codes, compression testing, etc.) as it could be mechanical, electronics or contaminated fuel