i was standing outside minding a nice leaf and branch fire in my fire pit when my son cranked up his cold 300. it started harder than it should have, but then again it was about 15 outside. anyway, it did start and he let it idle while getting ready to leave and i thought i noticed it surging a little bit. i listened for a couple minutes thinking it would stop doing that as it warmed up but it still appeared to surge. i sat in the car and watched the tach and it was difficult to see how much, but near as i can tell it was idling at about 750 and would go up and down maybe 75 rpm every 5-10 seconds. whatta suppose could be causing that ? of course he left before it got to operating temp (actually it never does get warm until its on the road) so i am not sure it continued or not. we have not checked or adjusted the valves yet, and it does have one loud clakker or whatever its called when pistons are changing holes, and im still looking for diesel purge or something good to run thru the fuel system.
oh, and thanks for the good information about storing my extra IP i asked about this morning.
davidh

My engine was doing the same thing and I adjusted the rack damper bolt out a little on the back of the injection pumpand now it idles fine when cold.

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84 300 Turbo / 320,000
96 E300 D / 55,000

My 300 TD had the same problem and changing a glow plug solved the problem ...... idle issues, hard starts, etc. are usually related to the glow plug system... engine surge at start up is incomplete combustion in the cylinder causing the drop and rise in rpm... When the combustion is complete, smooth idle is present like in a warm engine


Bill
1981 300 TD