I have a 190E and just went throught this same problem for about a month.

Previous thread hinted towards idle valve. this is true but before you replace it try the following. This is what I did.

Take off the air filter housing and cover up the air intake hole. Im my case the idle screw was sticking took a approved EFI cleaner like carb cleaner and just put a dropor squirt in the valuve stem hole then used some compressed air to clean out some sand or dirt type material shot out several times do not put to much cleaner or air in the valve. just enough to clean it out. make sure screw inside moves up and down smoothly. Also behind the battery compartment is an altitude relay???? it will have a 10 amp fuse pointing towards you This relay can make the engine cut out for some reason. I took mine out and blew compressed air in the pin holes to clean out them and the relay switch again be carful not too much air only enough to clean not to damage. Can't say for sure it will help but I have not had a problem since and this was what I did. P.S I had the exactly, I mean exactly the same problem you are describing.

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