Smoke on "Heavy" Acceleration - 1998 E300D-T - How Do I Clear This Up..Italian Tuneup - PeachParts Mercedes-Benz Forum

RLGDiesel · #1 05-20-2007, 06:22 PM

I purchased my 1998 E300 with 16K miles in 1999. Since that time, I have put 63K miles of primarily city driving (with a few long summer trips) on the car. I change the Mobil 1 5W-40 every 5K miles religiously. Driving to work and back (about 12 miles), I rarely push the engine above 3K RPMs. This weekend, however, I noticed a large cloud of black smoke while merging semi-aggressively into traffic. I accelerated subsequently harder to see if it would happen again, and each time the engine was pushed to about 3.5-4K RPMs, smoke would appear (during the daylight, by the way...not in the headlights of cars behind me). I have read that sometimes the hardest driven diesels hold up the longest and that the Italian tuneup is not always a bad idea. Is black smoke normal from a well-maintained, calmly-driven OM606 E300D-T? Also, What is the proper way to burn off these "deposits" - for example, is using gear (3) instead of (D) on the highway for about 5-10 miles sufficient to "clean-up" the engine? Is there any risk of harming the engine or 722.6 transmission in this vehicle...Is an Italian tuneup beneficial on a newer diesel like the 1998 or more suited for W123 OM617s? Sorry for the long post and maybe frivolous concern.

stcbenz83 · #2 05-20-2007, 06:36 PM

Black smoke indicates unburnt fuel

You could also try doing a diesel purge

F18 · #3 05-20-2007, 07:25 PM

RLGDiesel, I drive almost all highway miles......and all my past and present diesels smoke under hard acceleration and especially when dropped down into "passing gear". As stcbenz83 said its unburned fuel.....combustion efficiencey drops significantly when accelerating.

I think an "Italian Tune Up" won't do much unless it is accompanied by some sustained highway driving to burn up the excess fuel and any carbon that might have been blown loose.

If your routine driving is mostly city then you would probably benefit more from an occasional Purge treatment than just wasting fuel for a quick blast.

nhdoc · #4 05-20-2007, 08:05 PM

I'd second the diesel purge since you probably have injectors with poor spray patterns due to fouling. When I bought my '98 in late '04 it had 115K miles on it all easy driven. It took a year of aggressive heavy footed driving to clean it out.

Mileage went from 24-25 MPG to 29-30 MPG over the first year and that smoke the first time I redlined it could have caused people following me instant lung cancer. Now, 30K+ miles after I bought it the car runs better than it ever has. These cars like to be driven harder than most of the people who owned them did. I'm sure my intake, injectors and exhaust were carboned up good by the PO, but now all is clear and clean.

TheDon · #5 05-20-2007, 08:12 PM

Do a diesel purge then run a can of BG44K in the tank once and a while..

TMAllison · #6 05-20-2007, 08:22 PM

My experience was similar to Marty's when I first got mine, although my mpg's did not start out as low.

Was a lil embarrassing early on in my ownership when being sporty while merging into traffic but made merging easy because the second time you looked in the side mirror there was always a hole to merge into...

I've recently done DV seals and run 4 cans of DP through and now I have difficulty getting any smoke at WOT which I miss as it was a wonderful deterrent to tailgaters.

RLGDiesel · #7 05-20-2007, 09:22 PM

Thanks...I'll search for more replies on Diesel Purge, but does anyone have a brief usage summary (How do I safely run the product through the system? Are there any things in particular I should watch out for?)

TMAllison · #8 05-20-2007, 09:51 PM

It's very simple. You need two 3' pieces of hose and a pop bottle.

E300TD diesel purge proceedure solved!

If you have an old plastic fuel line you can cut one end off of it is even easier.

Parrot of Doom · #9 05-21-2007, 06:17 AM

You're replacing fully synthetic oil every 5000 miles?

Thats a big waste of money. You could treble that interval without problems.

Engine RPMs, not exceeding 3000 while cold is a good idea, but theres no reason not to exceed it when the engine is up to temperature.

The diesel purge isn't a bad idea, personally I don't think it will achieve that much compared to having the injectors cleaned. I would consider checking the air filter condition, and also cleaning the MAF element.

Using 3rd gear instead of D won't do much. You'd be much better advised to get that turbo spinning, and the best way to do that is by giving it some serious beans every day