M117 - Engine shake at idle

[6.9forever]

My 117.985 engine in the 450SLC idles quite smoothly at the specified 750 rpm and normal temp (87C), but it shakes and vibrates the body (e.g. sitting at traffic lights). Is this an engine mount problem or other?

Look forward to members' expertise.

Thanks.

 

[abl567]

Are you in neutral for the smooth 750rpm idle and transmission engaged at the lights when the shaking and vibration occurs?

 

[6.9forever]

In Drive, with foot on brake at lights, Anthony - shudder occurs. Revs go up when in Park or Neutral. In P or N I'll re-check what happens with shudder.

 

[6.9forever]

Yep shudder is there when stationary in P, N or D. Just a bit rough, not smooth even though revs look healthy.

 

[c107]

Have you checked the suppressors at the end of your spark plug wires? My rough idle was caused oxidized suppressors causing a weak spark.

 

[Styria]

Hi 6.9 forever, initially I would start checking high tension leads and suppressors. As well, how about spark plugs - how old are they. Maybe this is a car that's not being used much and has probably never had a lot of time spent on its mechanicals and state of tune. Regards Styria

 

[6.9forever]

Thank you for the "lead" ... (get it?) LOL. I'll make some investigations.