Engine Revving on it's own

[EvianBaby]

When I was sitting in traffic last night I noticed my engine appeared to be revving of it's own accord. Only up to 1,000 rpm every ten seconds or so.

Is that normal?

[EvianBaby]

Thanks Al! At least I know it's probably not something major that I need to worry about. Will get my mechanic to have a look at it next time he's doing something.

[MantaRay]

I'd be tempted to stop the engine, disconnect the battery for 2-3 minutes, reconnect the battery, restart engine, and see if it settled down to a steady default idle setting again. Radio code/radio stations/clock time etc will need resetting afterwards.

[AlBags]

Well that's an attempt to dump any minor codes .. although major ones tend to get locked in (depending on ECU) .. then a relearn.
Used to work nicely on old Motronic .. but not much of Euro4 level onwards.
Relieves symptoms without looking at source of problem tho .. Often the problem will return.