This is an intermittent problem which has been noticed over the last week or so. Prior to that the car was running great and I’d covered over 600 miles the previous weekend.
Basically the car starts first time every time from cold or hot and idles smoothly.
When driving, the car will suddenly, without notice take off. This happens with or without pressing the accelerator pedal. The engine surges to 5,000rpm, I brake, then the engine dies.
The car is a UK model and I’ve noticed the ASR light comes on when the problem occurs.
I’m quite handy mechanically and don’t mind working on the beast as long as I can find the things to check, so may need some guidance there.
Any ideas what to check?
Thanks in advance

I hate to be the bearer of bad news but your car has what is known as an ASR 1 system. This was before they were thoughtful enough to have built in diagnostics. They are a nightmare to diagnose, and I try to hide in the shop when one comes in. You have to do a breakout on the abs and asr modules looking for problems hoping to find one, with no guarantees. So what I'm getting at is that a mercedes tech with all of the special breakout boxes and cables and a lot of know-how has about a 50% chance of diagnosing a complex ASR 1 problem. Take that for what you will. At the very least it may be worth it to pull the connectors from the module, the actuator, and potentiometer to make sure corrosion hasn't crossed the circuits inadvertantly powering up the actuator.

Thanks for the prompt reply.
Without doing anything to the car, I took it for a test drive to try and gain a few more clues.
When starting from cold, the idle speed seems ok, but when starting from hot it can be anything up to 1,500rpm.
The surging is now happening all the time and I noted exactly what happens.
After selecting drive and setting off, the ASR light appears after a couple of seconds. The engine surges (revving to 5,000rpm) after I press the accelerator pedal, then immediately dies.
The revs fluctuate between 0 and 5,000rpm a few times before the engine will die completely.
Are your initial diagnoses still valid? If so, where are the components you mention? I can see the ABS/ASR module but not sure about the actuator and potentiometer.

I had a look at the car tonight. All wiring seems ok around the ABS/ASR module and no vacuum pipes are leaking. I removed the air filter and housing to check the accelerator linkages, which again seem ok and not snagging on anything.
I’m not sure what the last part is, that’s connected with the linkage. Is this the ETA? It has VDO stamped on it. On my car which is a UK model, looking in the engine bay, it’s located on the left hand side towards the front of the car, above the alternator and behind a water hose.
When I switch the ignition on (but without starting the engine), there is a buzzing sound which may be the fuel pump so may not be connected to this asr fault.
I disconnected the linkage to the ETA – if that’s what it is.
The car starts ok and ticks over at about 2,000rpm. Although the linkage is not connected, the ETA lever moved backwards when the engine started. I then tried to manually move the ETA lever forward. There is a bit of resistance, but when it did go forward the engine died.
Does this information lead to any further conclusions? Any else I can do or check? Are there any decent engine diagrams anywhere?