Ive got a 86 300E and it has a straight forward after starting climb to 1200 rpms and that is it. I bought a new idle control valve,but havent put it on yet as i was told that it could have a vacuum leak at the vacuum modulator. I havent checked it yet,but i really dont think so.Is their another way to check to see if the idle valve is defective? If it isnt the valve i can take the new valve back.