I have a 1990 500sl. Runs great when warm. When cold it starts fine but will hardly come off idle. When you push the gas pedal it coughs etc. If you let it idle for a minute or two it runs fine. Like a carb car with a stuck choke! My conclusion is that cold run mode is wrong.. I pulled the cold start valve out and it doesn't seem plugged. Olease offer any ideas

thx