E320 stall in cold weather
 

My Mercedes dealer was unable to diagnose a problem with my well-maintained 2001 E320 wagon I have during the winter. It has 150,000 miles.

When the temperature is below freezing, the car starts fine, but stalls once I put it into drive, even if I let it warm up beforehand for five minutes. It takes another five minutes or so before the car will keep running once I put it in gear.

I once let it run a full 15 minutes before I put it gear. It tried to stall even then, but didn't. Once the vehicle drives off, there's no problem until the next morning.

The dealership says it is NOT the cold start valve. No error codes appear, either. They raised the scary prospect that it could be transmission related, but it was just a guess.

Any insights?

Dealer techs are complete idiots. Remove and clean your throttle body.

Thanks ... would be great if it is that straightforward. Could you elaborate? Why wouldn't it generate an error code?

Because there's nothing wrong for the ECU to detect. The dealer tech was simply being lazy and possibly stupid. The engine needs more air and fuel when it's cold. If your TB is gummed up with years of crankcase blowby the moment you go into gear the TB has to open up a tiny bit to let in more air to compensate for the change in load and maintain idle. If that tiny gap in the open the is taken up by deposits the engine stops. The engine doesn't know why it stopped so it won't store any codes. This is the point where a competent tech would look at engine live date and check engine coolant temp, intake air temp, MAF sensor flow rate. A bad temp might read higher than actual temp which could cause the engine to stall. A competent tech would remove the intake tube and visually inspect the TB . Unfortunately you ran into an idiot. I can't believe a dealer sent you home with
https://media3.giphy.com/media/3o6Yg...CVq/source.gif

If you don't work on your own car find a competent MB independent shop and avoid that dealer. With just a minimum of effort they should be able to figure this out. My guesses are dirty throttle body, bad engine coolant temp sensor or bad MAF sensor in that order starting with the least expensive option. Good luck

What t said - clean throttle body. Pretty straight forward job.

Another symptom of dirty throttle body (specifically on BMWs) is that as you come to a stop and the car idles down it becomes real rough and almost shuts off before it settles down.

I’ve come across this exact issue several times over the years. The problem is a faulty torque converter.

I would definitely clean the throttle valve since it’s quick and cheap, but I doubt it will solve the problem.

Does it jolt to a stop when putting into drive or reverse? Or does it just calmly shiver and shut off?

mot
 

mot valve also unhook lines spray cleaner,and let set

I have seen this issue too, torque converter clutch was locked on. replaced with rebuilt one with the sonnax kit already in there, And that car shifted nothing short of magic level good.

Some people on the internet are complete idiots. This car uses a drive by wire throttle and does not have a hard throttle stop for min air nor an idle air control valve. This means that even if the throttle blade is sludged up, the computer will command the throttle to maintain proper idle speed even under load.

As others have stated, it is likely the torque converter clutch sticking on when cold. You are also likely to have somewhat rough down shifts when coasting to a stop and a light throttle vibration around 35 - 40 MPH.

Have a look at the attachments in post 3. https://www.peachparts.com/shopforum/tech-help/349697-engine-stalls-when-cold.html

Also go to the SONNAX web site and look up info on the 722.6 Mercedes / Chrysler transmission.

Are you daft or something? A dirty throttle body absolutely will cause a stalling cold weather that's why Mercedes put out a TSB about this very issue on the m112 and M13 engines.

And no the sonnax kit won't fix this issue. The TCC problem does not cause stalling in cold weather.

.....idiot....daft......reminds me of Thanksgiving dinner at home with the family:)

Actually the torque converter can cause a cold stall. That's what Sonnax calls the problem.
https://www.sonnax.com/tech_resources/22-mercedes-722-6-cold-stall-tcc-shudder-part-1

Many things can cause the engine to stall including a dirty throttle body. It would be stupid to jump to the conclusion that it's caused by the torque converter lock up when the OP doesn't list any of the other much more common symptoms related to the TCC circuit. On the other hand cold stall is a known fault on these engine when the TB is dirty and far easier to fix.

Like I said it is easy to clean TB on this application. That is what I would do first.