300E Stalling
 

This seems to be a common problem but after reading the posts, I am still puzzled.
My problem is as follows:
cold star perfect, idle normal driving for first 20 minutes flawless. At about 20 minutes, sputtering begins ususally at lower speed deceleration or at idle until engine sputters out. Then no success on restart, cranks fine.

Check for spark on craning, it does exist.

5 hours later, start car and drive away flawlessly for another 20 - 25 minutes.
Played with 2 different mass sensors, same issue, cap seems fine as does rotor.

Somehow If I have spart on crank would it rule out crank angle sensor, coil and OPV?

The car has 170 K kms.

PS Before this happened on warm start up after being run to full operating temp, it would after hot soak start with a little miss and 3 seconds later clear up and idle smoothly. May not be realted but.....

When was the last time you checked/replaced the distributor cap/rotor?

The same happened to my 1991 300E (long gone now) and I chased a lot of things and it was finally the cap/rotor.

Check the easy stuff first like the cap, rotor and coil but in my case (91 300TE) the crankshaft position sensor tested fine but was indeed defective. My vehicle had spark too but was triggering at incorrect time. Good luck. Mark

Re rotor and cap; There should be tell tale cracking and carbon tracking if the cap and rotor are bad. What am I missing? Is there something that is inherent to create this problem outside of what I just mentioned?

My 300e stalls belows minus 10 degrees celsius,occasionally only once to twice per year.
MB mechanic adv not to fix it.Diagnosis by MB or parts cost more than the car

In my case, the contacts were worn (frictional force chewed up the material a bit) so the rotor was not making good contacts with those on the cap, especially when hot (the cap must have been expanding a bit more than the rotor so the rotor cannot make good contacts.

Once I took the cap out and the wear was quite obvious.

Your case might be different but it is possible if you did not remove the rotor to check the inside.