VW Polo rough idle.

[Godecks]

Our 2010 VW Polo 1.6 tdi runs and performs well, but occasionally has an extremely rough idle causing significant vibration and the revs rising and falling.

Strangely turning on the heater blower causes the revs and idle to return to normal, turning it off causes the rough idler to return instantly.

Has anyone experienced anything similar or have any idea what might be causing this?

[E-bmw]

What are the conditions in which it is prevalent?

Adding electrical load like you are suggesting will increase idle speed on many engines to cover the increased power consumption from the alternator.

[Godecks]

It's when the engine is at full operating temperature and really seems to struggle, there is a lot vibration and fluctuating revs. As soon as the heater is switch on it idles perfectly. I"ll try other electrical laods to see if the effect is the same.

[Demelitia]

Is the alternator belt and tensioner jumping about when this happens?