I drive a 2003 Polo 1.6 the car starts properlysometimes but then sometimes its starts very funny as if its suppressed air inside.and then it lacks power the revs are low and after a while it comes back again.onther ocations it would be driving perfectly and all of a sudden start sounding funny idling too low or idling indicator going up and down just a little bit,then it start losing power.

SOURCE: vw polo 1.4 tdi idle problem

Hey.. i just had this exact problem in my GTI and after 2 weeks of trial and error, I had to replace my Coolant Temp Sensor.. it was bad so it threw off the fuel metering valve which was part of the crazy idling problem.. I cant be 100% sure because our cars are not exactly the same but I mean we have the EXACT same symptoms so .. justa suggestion. Use the VAG-COM sensor reader and you'll be golden.

SOURCE: volkswagon bora 130 tdi is juddering with asr

asr works in conjunction with abs.to stop a wheel it(the car)thinks is loosing grip, from spinning.By applying the brakes to the wheel that is loosing grip,so the car is applying the brake. hence the juddering. if it stops when you turn it (asr)off it must be a sensor fault.easy way is to plug in the diagnostic computer to pinpoint faulty unit. if you dont drive very enthusiastically,then turn asr off until next mot/service.get back if you need any more info ....

SOURCE: vw polo 1997 999cc often idles eratically

First- lets change engine coolant sensor/ECT/ and you will be very surprised.Black head with four pins.Be very carefull when change it because there is pressure into coolant system.First-open slowly the cap of engine coolant tank.Then tighten again to safe coolant.Unplug the sensor,remove the pin and pull out the sensor.If the "O"ring/old one/ is still inside-take it out.