Have a minor problem with an old M410+.

When down to temperature on low speed the throttle solenoid engages approx. every 5 seconds runs on hi speed for 1 second then drops to low speed again.

I seem to recall many years ago having this problem on a Mistral and it was down to a bad engine earth but have ruled that out on this one.

It's not a major problem but is bugging me any ideas?

Regards,
djbe.