I have a new 350 sdl with a surging idle
 

Hello, I have a newly purchased 1990 350 sdl. It has a surging idle. What should I check? Thanks.

This doesn’t have much to do with performance or an existing thread, woukd be better in the regular diesel area.

350SDL has a rudimentary idle control in it. But before that, what history on the car do you have? Condition? Pictures? Location? What services were done recently per records, or have you done on it?

Once you’ve verified reasonable fuel filters and hoses, linkages all moving well, etc., you can consider the system. Pull the ELR connector on the back of the IP. Any change in rpm? What is your rpm before and after? Report both back here. What happens if you give a tiny bit of throttle? Does it smooth out? Coukd be a base idle set too low.

Give some looks over the engine, do those steps, and report back…

If you unplug the ELR actuator on the back of the injection pump does it idle smoothly (at ~500 rpm)?

-J