Like it says; 91 350sd, 603 engine. Hold on a minute before you start bashing the 603 and referring to it as the rod bender!
This has been a good engine. Just recently i've developed a slight hesitation when your cruising and then coasting to slow down, as you gently start to accelerate I can feel a slight hesitation; like when the fuel filters need changed; but I already changed them. No vac. lines off.
I'm coming due for the timing chain replacement and I'm asking the experts if this could possibly be an indication of chain stretchage affecting the timing as the throttle is advanced.
thanks in advance for any good advice.

Definitely the rods

Until the experts show up, here's my take:

I wouldn't expect the chain to cause hesitation when coasting or gently accelerating. As the chain wears and IP timing slips, there'll be a general loss of power. Across the board. There's a centrifugal advance mechanism in the IP timing sprocket. IP timing will advance with engine rpm even with a tired chain.

I don't subscribe to 'coming due' for a timing chain. It's within spec or it isn't. At best you've noted a trend over a series of documented checks showing it's about to cross from being in spec to out of spec. Even MB that has a service interval for brake fluid and fuel cap gaskets has no time or mileage interval for replacing a 603 timing chain.

I would guess the hesitation is more related to the injection subsystem. Maybe you do a lot of short trips, stop and go driving and sitting in traffic. An Italian tuneup should blow out the cobwebs. Consider also a bottle or two of Diesel Purge.

Since you mentioned vacuum lines, maybe the EGR valve is stuck open. Maybe the turbo impeller isn't spinning as freely as it should because of bearing wear or coked oil.

Sixto
87 300D

Hesitation at 65mph with the cruise on was my first symptom of a failing injection pump.

__________________

Present
1987 300SDL
1991 300SL
1990 560SEL
2001 ML320

Past
1969 200D 1979-82
1983 300SD 1984-85
1972 250C 1982-02
1995 S350 2011
1997 S320 2012

Sixto, I had thought about the EGR valve a little bit. I'll have to pull it off and also check the turbo to see how freely it spins.
I've been wanting to remove the EGR and install blanking plate. Maybe its time.
The hesitation is felt at slower speeds. At 65 on the highway, its not really noticeabe.
I really don't do short trips. 45 miles to work in some stop and go (stoplights). The trip home is freeway, 40 miles.
Thanks for the info.

I can't believe I'm not getting any more input.