1989 300 te- Last summer/ fall, I had this stalling problem. Whenever the rpm's would drop to idle, I ran the risk of the engine just stalling. The rpm's would drop below idle for a second and not recover. There I am, stuck at a light, on a turn, etc....having to throw it into neutral and start the car. Then, as the temps dropped outside, the problem vanished. I forgot about it. Now, in NY, the temps this past weekend were in the 50's-60's...problem re-surfaced.
WHAT IS IT? HOW DO I FIX IT?

Check fuse in OVP relay beside battery to start with...

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2009 Mercedes ML320 Bluetec

1990 300TE, same problem. Change the coolant temp sensor and make sure the proper spark plugs are installed, many idiots will put Platinum plugs in, wrong....but the coolant temp sensor is very important ($35). these 2 items completely solved my very same problem, the Bosch Copper Pluses are around $3 each so the whole thing could be less than $50 out the door. Also, make sure the hoses are all OK.....

Test your fuel pressure. This must be a must for anytime a car stalls just to take out the CIS out off the equation.

How do I DIY check fuel pressure?

Get a CIS tool