Driving my '85 300D yesterday, I turned the corner onto a another street, stepped on the throttle (nothing dramatic but a good solid 1/2-2/3 whack of the pedal) started revving up in 2nd and I heard a very metallic-y rattle/clatter. Last about 1-2 seconds, and was followed by what sounded like a nut or something making it's way down the exhaust pipe, then went away. I looked in the mirror and noticed a big cloud of black smoke behind me. I never noticed a drop in power or anything...if not for the noise and then my glance in the mirror I'd have no idea anything "happened". I drove on very gingerly, but as all seemed OK I returned to normal driving after a few miles.

Everything seems normal now, but I wonder what the heck that was? Anyone have anything like this happen? Could that have been a big chunk of carbon breaking loose and getting spit out?

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1985 300D 231K anthracite grey w/black int.

What happened was a momentary malfunction of an injector. Could have been caused by a speck of carbon or the pintle not seating properly. This is not uncommon in diesels and is usually insignificant. If it reoccurs on a frequent basis you will need to have the injectors pulled and pop tested and most likely rebuilt. HTH

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Retired
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"Without Fleet The Pride Doesn't Ride"

1983 300SD 609K + still going strong!
1970 Monte Carlo
1994 Ford F150

Injectors sounds right, but check your oil. Part of the turbo may have blown off and down the exhaust pipe(worst case scenario)

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$60 OM617 Blank Exhaust Flanges
$110 OM606 Blank Exhaust Flanges
No merc at the moment

In Trade School they said small pieces of the Fuel Injection Hard Line can erode off from the inside and get into the Injector. If you have noticed the inlet on Mercedes Injecters there is not just a hole. That thing in the hole of the Injector Inlet is a Metal Edge Filter to prevent anything really big from getting inside.
The Injectors on my Volvo and the VW Rabbit Injectors I have seen do not have that filter.

Any possibility that a piece of his Pre-chamber came off and that is what passed down the exhaust.
Or maybe one of the Pre-chamber holes got plugged for a bit.

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84 300D, 82 Volvo 244Gl Diesel

Depends on the injector. Later ones just have a single hole.

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine

Perhaps a chunk of carbon broke loose. Do you drive like a granny usually? If so, you may have a carbon-built up engine....and it was hacking out some junk. Perhaps it needs some Italian tuneups.....

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-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)