My 93 D350 began idling at 1200 rpm about a week ago. At first, cold idle was fine but went to 1200 (estimated) after warm. The past few days it idles high all the time. All of the linkage is in place and tight.

A second symptom appeared when the high idle became constant: When turning off the engine, the engine chugs at 250 rpm and then finally stops after 5-10 seconds.

I'm thing something in the injector pump is amiss but don't know my way around the pump. Ideas and suggestions please!

 

Problem solved. Very technical. Jam nut backed off on idle screw letting it back out. Geesh.

 

Gotta love an easy fix!