Took my 420SEL with a cold start and idle problem in to be checked out; came back running a lot smoother. Turned out that I had three vacuum leaks; one was at the idle speed control valve that I just replaced and there were two disconnected hoses, located behind the passenger headlight (switch-over valve for the air injection? Two light-blue, small diameter hoses, one with a red stripe and one with a blue stripe.)
Additionally, the tech reports that it had incorrect spark plugs (he replaced all eight) and the #3 spark plug connector was not on tight and had minor ‘corrosion’ from arcing. Definitely runs a lot smoother and started with the first key-turn running errands on the way home. I’ll find out tomorrow morning how she does on a cold start.
The tech also recommended that I replace the old style metal injectors and recommends replacing them with the newer copper style injectors, along with the seals and stands, whatever that might be. Is that a DIY project?
Richard / E320