The difference a clean stepper motor makes .......

[M J H]

In 18 months of ownership and at least 2 requests to get the main dealer to resolve variable/hunting revs, mainly taking a while to idle back to 1000revs. Decided to actually do something practical with the Bible rather than just read it...so with newly acquired large adjustable in one hand and book in the other, performed what turned out to be the simplist of tasks, producing the most remarkable improvement.
Drives like a different car now, amazing how you get used to and compensate for bad running etc.
As you can tell I've virtually nil pratical understanding of these matters, yet was able to resolve this , where the main dealer seemed unable.
I've read on more than one occassion the cry " clean the stepper motor" in answer to idling problems,but had always assumed my problems were far more complex, and way beyond me.
Anyway having taken this small step in underbonnet fettling any comments as to how often this neads cleaning?