W203 surging when cold

[Silverbluemachine]

My W203 55 plate cd220 diesel is surging around 100 rpm at low load/speed (up to 40mph) whilst the engine warms up. Not noticeable on acceleration but then returns when at steady speed. Any ideas. Tia

 

[Petrol Pete]

'Surging' (slight rev change when cruising) could be the lock up clutch slipping . Does the car stall , or get close to stalling when coming to a complete stop , Is the fuel consumption higher than normal ?

All are signs of lock up clutch slip , unless of course your car has a manual transmission.

If automatic when was the gearbox last serviced ?

 

[Silverbluemachine]

'Surging' (slight rev change when cruising) could be the lock up clutch slipping . Does the car stall , or get close to stalling when coming to a complete stop , Is the fuel consumption higher than normal ?

All are signs of lock up clutch slip , unless of course your car has a manual transmission.

If automatic when was the gearbox last serviced ?

Auto transmission serviced 1500 miles ago. This only occurs when cold for around 5 miles or so. Can't remember it before the service but gearchange had become a little jerky hence the service. Super smooth gear changes since the service.