Initial engine hesitation, then RPM instability
 

Hello everyone, my 85 500sel is initially hesitant after startup, that lasts about 1/2 a block, then idles normally......it will then increase it's idle speed to about 1500, then revert to normal, and so on.....one or the other, nothing in the middle.........I thought the injectors might be dirty, so I bought a can of Techron to put in the gas, to no effect........any thoughts?