1992 190e will not idle when warmed up

[dennish]

2nd time with this problem. Last time it was a bad potentiometer that was the cause. I again changed it out with no luck. I had a spare Idle control valve, so I changed it out. No luck. OVP is quite new (maybe went bad??) What else could be the cause. Starts up when cold and runs good, but after about 5 miles. it idles poorly and dies. It will restart, but won't idle.