My '82 300D engine idles very rough after coming to a stop from normal or high speed running. It usually smooths out after a few seconds or if I step on the gas and get moving again.

Is there an adjustment or something needing to be replaced to fix this problem?

Thanks for any help.

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AJ
82 300D
81 240D
76 450SE
86 300SDL

Hi,

If it idles rough as in speeding up, then slowing down, then fast, and "hunting" back and forth, usually when hot after a good run, you might want to adjust the injection pump fuel rack dampening screw.

Make sure the engine is hot when you adjust it.

You will find the screw at the back end of the fuel injection pump, near the bottom.

It's actually a bolt. I think the bolt is 13 mm (head) and it will have a lock nut 14 mm, to prevent it from loosening.

With the engine hot and running, unseat and hold the locknut using a 14mm open end wrench, then gently turn the bolt in very slowly (use your fingers or a 13mm box wrench), and listen for the engine idle to smooth out and increase slightly.

Stop turning when the idle is smooth without going in more than necessary. If you go in too far and the idle gets worse, just turn it out till it sounds best.

Please make sure you tighten the locknut when your done.

Also, next time you replace the fuel filter, fill it with transmission fluid before you install it, confirm with your garage if you have any questions about this.

Hope this helps,
Acky