Both my 91 420SEL and 85 380SL were having the usual stalling issues. They drove fine but when I was comming to a stop the RPM's would drop below 400 sometimes it recovered and other times it stalled. Hot, cold A/C on or off it didn't seem to matter. I'd say it stalled between 10 and 50 times a week.
One day I went for a ride iin a friends Audi RS 4 wagon (oh my what a car!)When we stopped for fuel he put in the 103 octane and we had a long conversation about fuel quality effecting performance blah,blah,blah. Finally I put in 1/3 a tank of racing fuel mixed with 2/3 91 the car ran great and the stalling all but ceased at the next fill up I put 1/4 tank 100 octane with 3/4 91 occtane. That was 2 months ago since then I have been running 91 occtane and the stalling problem is 99.99 percent gone.
Just my experience

Does anyone have an explanation for this?

No, but i'd check the idle air bypass valve to make sure it's not stuck and is actually working.

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Regards

Warren

Currently 1965 220Sb, 2002 FORD Crown Vic Police Interceptor

Had 1965 220SEb, 1967 230S, 280SE 4.5, 300SE (W126), 420SEL

ENTER > = (HP RPN)

Not part of the in-crowd since 1952.

thank you.
where would i find this part?

Has anyone else tried this?

I guess the racing fuel mix and octatne 100/103 worked as Fuel injection clearners and cleaned your cars intake, fuel injection etc thus curing your issue. Most probably it was dirty injector and the spray pattern was not even at idle.

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87 420 SEL
Looking for a nice mid 80's MB diesel.
87 BMW 528e (Sold)
99 TOYOTA 4Runner
1989 Honda Accord (Sold)
1988 Honda Accord (Total)