Hello.
I've got a '96 E300D with 258K on it. I have replaced the glowplugs, decarbonized the intake, and used Diesel purge. Both fuel filters up front have been replaced.
The car drives fine BUT, at about 60C on the temp gauge(or 5 minutes or so on the highway) I get a plume of gray smoke out the tailpipe for about 2 seconds, with a small about of chattering. Then all is fine. For the rest of the day. This just happens when the engine is started for the first time in the morning. Temperatures outside are 25-50F. While it doesn't happen every single day, when it does it is extremely predictable, happening at about the same place on the highway(my way to work). Speed is generally 50-60 at this point.
Interesting fun fact: I was having a LOT of problems with surging on the same way to work--having to vary my pedal to get it out of the surge "point", up or down. Someone on the forums suggested I disable the EGR for testing. Using a method I found on the forums, I have disabled my EGR temporarily. No more surging. Very smooth. But here's the kicker: Before I did this, the gray smoke/chattering still happed at the same point of the drive, except it felt like the car was going to die. Now, with the EGR disabled, I almost feel like I'm getting a bit of overfueling, with no surging but still the smoke and chattering.
Any ideas? Injector? Intake flapper on drivers side under intake?
Thanks
jeff

Im betting on intake flap.

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1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42

There's also a "pressure control" flap just ahead of the EGR valve. With EGR disabled during your testing, there's no need for this flap. Look inside the pipe after removing the rubber accordion hose from the air filter and you will see the flap, held to a rod with two Phillips screws. Remove the screws and you can wiggle the flap out. Leave the flap actuator in place so the flap can go back in after the testing.

Jeremy

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

There's also a "pressure control" flap just ahead of the EGR valve. With EGR disabled during your testing, there's no need for this flap. Look inside the pipe after removing the rubber accordion hose from the air filter and you will see the flap, held to a rod with two Phillips screws. Remove the screws and you can wiggle the flap out. Leave the flap actuator in place so the flap can go back in after the testing.

Jeremy

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

I'm gonna try removing the EGR flap. The last 2 days, it did NOT smoke at all anytime. Running smooth. Will also verify other flap under intake.
Thanks for the answers.
jeff

Update: Sitting at a light in traffic at the "specific temp"(60C on the gauge), the smoking started. First time that I wasn't doing 60mph. Engine missing, tranny not engaging properly, "hammering". I've got to get the computer on this.

No flaps have been removed, just the EGR has been temporarily reassigned.

This is still very strange. What "kicks On" at 60c--or close to it? Lean to rich, rich to lean, no choke here, ?
jeff

I had a similar issue on my '95. (NA 606)

During (our admittedly mild so-cal) winter, when driving & warming up from a cold start, it would (at a specific temperature that I don't recall - maybe 50C?) feel as though it was running out of fuel for about 30 seconds or so. It was so bad that the engine almost stalled on a few occasions.

I knew my fuel lines were in perfect shape, so I hypothesized that the fuel thermostat was the culprit - when it hit the switchover temperature (?), the fuel flow seemed like it was temporarily restricted or cut off, possibly starving the IP. As the heat soak continued, the thermostatic element would continue to move to its 'warm' position, and all was good again.

That's my theory, but it remains speculation as I never got to prove it - the problem miraculously "cured" itself after a few weeks. Of course now I've jinxed it, and with winter setting in now...

__________________
Current rolling stock:
2001 E55 183,000+ Newest member of the fleet.
2002 E320 83,000 - The "cream-puff"!
1992 500E 217,000+
1995 E300D 412,000+
1998 E300D 155,000+
2001 E320 227,000+
2001 E320 Wagon, 177,000+

Prior MBZ’s:
1952 220 Cab A
1966 300SE
1971 280SE
1973 350SLC (euro)
1980 450SLC
1980 450SLC (#2)
1978 450SLC 5.0
1984 300D ~243,000 & fondly remembered
1993 500E - sorely missed.
1975 VW Scirocco w/ slightly de-tuned Super-Vee engine - Sold after 30+ years.