C280 V6 Automatic -Throbbing Tickover

[AlanGS]

At irregular times when cold or with sudden stops the engine throbs or hunts when stationary and in gear. The revs increase and decrease a few hundred revs which makes the the car vibrate unless the foot brake is applied fairly hard. If you shift to neutral the revs will drop and be stable.
I have wondered if the throttle cable is sticky. Any ideas

 

[television]

At irregular times when cold or with sudden stops the engine throbs or hunts when stationary and in gear. The revs increase and decrease a few hundred revs which makes the the car vibrate unless the foot brake is applied fairly hard. If you shift to neutral the revs will drop and be stable.
I have wondered if the throttle cable is sticky. Any ideas

Not sure off the top of my head if you have an idle relay, this could do it if you have one, these devices speed the engine up when selecting drive or when Climate comes on to prevent stalling, This is the only piece that know if you are in drive or not.

Malcolm