why do I have to slightly block open throttle body to get engine to idle

What is your question?

I changed out the cold start valve with a new one. Engine cranks strong but will not start until I slightly block open throttle valve. Then it idle and run as it should.But when I unblock throttle valve it shutsoff and will only start when throttle valve is blocked slightly open.......Need help bad...Thanks

What makes this problem better or worse?

Better when throttle valve slightly blocked open

How long has your 1990 Mercedes-Benz 300SL had this problem?

For a while ,car has been sitting for a year because of this problem.