Two new nagging issues
 

1992 300E with 44,000. I bought the car about a year ago with 35,000 miles. On cold start idle stumbles but does not die but very low idle about 500rpm or less. Becomes normal very quickly. Then the tranny does not upshift like it did before. I have to drive 4 or 5 blocks before it upshifts and then all OK.
After purchase, replaced injectors, seals, ignition wires, rotor/cap, temperature sensor and the OPR. Engine ran perfect until now. I have to drive 4 or 5 blocks before it upshifts and then all OK. All thoughts and knowledge appreciated.

Scrape the crust/crud off of the dist cap electrodes and see if that helps.

These cars have an upshift delay when the engine is cold. It forces the engine to rev higher which in turn gets the catalyst active quicker. Totally normal behavior.

Engine stumble when started that clears quickly is a hallmark of CIS injection. With newer injector nozzles, running some injector cleaner through it may yield some improvement but I wouldn't hold my breath.

I know the delayed upshift is normal for this 300E, but none of my previous MB's have had such a long delay. When I disconnect the vacuum valve electric supply the tranny shifts as normal. I assume the engine coolant temperature sensor sends the signal to the ECU and the vacuum is vented to allow normal operation. The sensor is only a year old. Could I have a sensor failure?