1995 E300D Auto Shift Fix - PeachParts Mercedes-Benz Forum

Wittenberger · #1 01-11-2007, 10:57 PM

Hi Everyone,

I have another fix for the archives...

The situation: My car wouldn't shift from 3-4 under heavy throttle. I first noticed it last week when trying to merge onto the interstate. Reaching for the floorboard with my right foot, I got good shifts from 1-2-3. But when it should have shifted into 4th, it kept holding 3rd and surging like it was trying to shift. It would only shift into 4th when I backed off the throttle. Around town, or in non-passing situations the car would shift 1-2-3-4 normally and downshift properly as well. Kickdown also worked well in all gears up to 64 mph.

I read some excellent posts on this forum re: diesels, 722 automatic trannies, vacuum circuits & measurements, bowden cables, and that excellent article by Steve Brotherton. I had to conclude that the transmission and control settings were OK. There was no flaring, no hard shifts, or improper shift points (except for the 3-4 shift under full throttle).

The fix: two new fuel filters. When my indy took the car for a spin (after checking the condition & level of the fluid), he agreed that the transmission was good. When he got to the moment of truth- the 3rd to 4th shift under full throttle- he looked at me and said, "The engine is bucking at high rpm when otherwise running smoothly. What causes that?" "Lack of fuel?" I replied. Bingo. He explained that fuel starvation prevented the engine from reaching the required shift point for a full throttle 3-4 shift. So all I got was a subtle bucking when the engine got ahead of the fuel supply...and no 3-4 shift.

The fuel filters did the trick. She runs like new now. I was surprised that they would need to be changed after only 11k mi ... but, then again, I'm new to this diesel thing.

Wittenberger
1995 E300D Blk/Blk 183Kmi

BioPOWER · #2 01-11-2007, 11:58 PM

606 filters should be changed at no more than 7k, IMHO. I just change mine when the oil is done; if you run biodiesel your filter intervals might be even shorter.

aklim · #3 01-12-2007, 08:36 AM

I suppose it depends on the fuel you get but they recommend change at 60K, IIRC and I change mine at 30K and they look pretty clean.

nhdoc · #4 01-12-2007, 08:43 AM

Yeah, the factory recommended interval is 60K miles, but mine got plugged up in less than half that, and this was only after a couple of tanks of ULSD...so what does that tell you?

The new fuels are really causing problems with filters and leaking fuel...once it is fully integrated and everyone fixed their cars it should be OK, but the filtration issue is certainly one that can be caused by the new fuel type. It apparently has addiditves in it that loosen up crud and plug up filters. You are lucky to have a skilled tech who recognized the symptom and got it fixed for you as economically as you did.

I remember being at a fuel station in sept-oct timeframe where the pumps were REALLY slow and the owner said it was the filters that were clogged and they had just changed them twice in the prior weeks...at that time I didn't put 2+2 together but it was just when ULSD was rolling out here as well.