Scirocco Central

2 possibly related problems. A sensor I think (airflow) has went causing the car to rev while idle, also the one that's stumping me is after about ten minutes or so a squealing noise starts. Gets quite loud and sharp but stops when accelerating. The tensioner has been replaced yesterday and its still happening. Not sure what it is..... any help appreciated. Trying to avoid a trip to the vw garage but its looking like my only option.

Squealing noise could be the auxiliary belt slipping.

ECU will raise the idle revs if the battery voltage is low to assist the alternator with charging. If the idle revs fluctuate erratically, that's normally a vacuum leak.

Yes they do fluctuate. I have just replaced the battery and since that the engine management light has disappeared, but idle revs remain

I just recently had revving / surging at idle.

did a bit of general research and checked with my local garage. It was the PCV unit. Changed that and the idle is like new, no surging, revving and very stable.

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