Okay, I know this is a shot in the dark, but I have seen some pretty amazing diagnoses on here...

Background :
85 300d has been sitting in the garage for months while I rebuilt the front end and did some other stuff. By the time I finished with all that the tank had grown a crop of gunk like you wouldn't believe. I pulled the tank and cleaned it and have been driving pretty regularly without problems for about 3 weeks. I was out of town for a week and a half so didn't drive it then.

I started it the other day and got a rough idle and it died. Started again and rough idle again, but seemed to smooth out if I stepped on the gas. Backed it out the driveway and drove around the block, but nothing much happened when I stepped on the pedal. Just limped along, then engine would rev and I would go. Since I had recently removed and cleaned out the tank, I figured that my fuel filters had clogged with some of the residual gunk in the system. I had a spare set figuring I would need to change the filters again soon, so swapped them out. I still had some hesitation from idle, but seemed drivable. After driving on the freeway for half an hour without issues, parked the car and then when I started again really bad hesitation. Step on the gas and almost nothing happens, but then when the rpms start to go up it is fine. Seems like maybe when the turbo kicks in it is okay, but at low RPM no power, no acceleration, and prone to stall out.
at idle the oil pressure gauge actually drops down to about 2!!
Idle is rough with some shaking. If I rev the engine up it smooths out.
By necessity, I drove it back home and again, once I got up to speed no issues. Seemed to have normal power at higher RPM.

I can see a bubble in the inline fuel filter, but just 1 and it pretty much stays put. I don't see bubbles flowing through the fuel lines.
It seemed to have a bit more acceleration from a stop if I manually put it into low.
Any ideas on where to start?
Why does it seem fine at higher RPM, but not at low RPM?

__________________
'84 300D Turbo Diesel
San Jose, CA

It does sound like a Fuel Supply issue.
It still could be an air leak somewhere. I had a small Air Leak at my Plastic Primary Filter due to the Hoses being Hard. You could tighten the clamps but the Hoses had no elesticity to seal well.
Then if you have the Old style shiny Aluminum bodied Hand Primer that could leak.

Just to see and because it is easy to do; try swaping the Fuel Inlet and Fuel Outlet hoses (you need at least 1/2 tank to do that) and see if it inproves.

Check your Linkages to the IP and see if something might have slipped. Hold the IP Throtlle Lever while someone slowly steps on the Pedal and see how much play there is in the linkage before Throttle Lever trys to move.
After that have the Pedal Pressed all the way down and see if the Throttle Lever goes all the way to the screw stop.

__________________
84 300D, 82 Volvo 244Gl Diesel

Selectively pulling out the relevant information would tell you that you don't have a fuel issue. However, this makes an assumption that it is "fine" at higher RPM's. The real question is whether it's high rpm performance is to spec..........or simply better than the low rpm performance. Understand that the low rpm performance will always be less than the high rpm performance due to the effect of the turbo.

A 0-60 time would confirm or deny proper high rpm performance.

If you don't have a fuel issue, your problem is likely to be IP timing and/or valves. When was the last time both of these were set? If not performed in the last two years, they're first up on the list.

try diesel purge, maby it sat with bad diesel, ital tune-up and clean it out and then change oil

__________________
1985 300D - 599,xxxk - blue interior #265 Monark Nozzle, AL129X, 15" Ronals, Gen II Big Brakes hunting
1985 300D - 491,xxxk - in prog-{A-A IC, 3" exhaust, psi\pyro, 28*BTDC, Hella Euros, IP Limiter removal
1985 300TD - 783,xxxk - parts car,used new engine with ALDA cap inplace
1987 Kenworth T-600 8LL 425 CAT Mech. - 6,000,000+k - DEI exhaust wrap, punched through resonators, 1 recent rebuild,

Thanks for the advice so far.

I am thinking I will diesel purge and see how it goes. During the diesel purge it will be running from (and to) the diesel purge jar without using most of the normal fuel lines so that should clean out any residual junk AND eliminate the possibility of air leaks over a good part of the system. Valves haven't been adjusted in a while. I've been wanting to get to that but haven't managed to get that far down the "to do" list so I guess that gets bumped up to number 2 (right behind diesel purge).

My 0-60 time would probably be measured in minutes, not seconds, but most of that would be 0-10, then okay from 10-60. It may not be performing to spec at higher RPM, but seems pretty normal. No trouble cruising at 80 uphill on the freeway (uh, I mean 65 officer )

__________________
'84 300D Turbo Diesel
San Jose, CA

have you cleaned the banjo bolt from the back of the intake?

__________________
1985 300D - 599,xxxk - blue interior #265 Monark Nozzle, AL129X, 15" Ronals, Gen II Big Brakes hunting
1985 300D - 491,xxxk - in prog-{A-A IC, 3" exhaust, psi\pyro, 28*BTDC, Hella Euros, IP Limiter removal
1985 300TD - 783,xxxk - parts car,used new engine with ALDA cap inplace
1987 Kenworth T-600 8LL 425 CAT Mech. - 6,000,000+k - DEI exhaust wrap, punched through resonators, 1 recent rebuild,