2007 MY08 1.9TDI POLO - erratic idle when changing gears to neutral at signal stops.

[JITHEN]

Hello all,

im noticing my polo 1.9tdi tending to have an erratic engine idle rpm when downshifting gears to neutral while coming to a stop at signal lights. The rpm at times tends to stick at 1200 -1400 rpm, at times its 1000 rpm, at times its normal at around 900-950 rpm.

When the rpm sticks above 1000rpm I notice that a light tap on the accelerator to rev the engine tends to bring the rpm back to 950 rpm.

This happens mainly during a hot summer day during the summer season and vanishes during the winter season.

It has run 63500kms and had its 60k service done 2months back.

what could be the cause of the above condition??

[nightphotographer]

First thing that comes to mind is the AC mis-behaving, strange it only does it in summer...if it was anything else you'd expect it to do it when it was cold. Doe it do it when the AC is switched off?

[JITHEN]

It does it both with aircon on and off.

[gldgti]

could be a lot of things really - probably it would be good to get it scanned. might be a fault with the egr flap, oil vapours due to hot weather running, etc.... when was the oil last changed?

[JITHEN]

engine oil n filter along with air filter was changed at 60k service.

[nightphotographer]

And you used VW Spec PD oil?

The reason I ask is, when I was in the UK I was sold VW spec non-PD oil for my 1.9 PD TDI Fabia VRS, it blew a turbo manifold gasket as soon I drove it and the garage felt like absolute noobs - got it repaired, flushed and replaced and whatever else because of it.

[JITHEN]

yep castrol synthetic long life vw specs oil.

[nightphotographer]

Is that definitely PD oil? Castrol recommends "CASTROL EDGE PROFESSIONAL LONGLIFE III 5W-30" - is that the one you used?

[JITHEN]

yep thats the one. picked up the 5 litre can from the dealer barloworld vw.

[nightphotographer]

just checking Yeah I have no idea, like gldgti says it could be anything and everything I've suggested that's caused problems for my diesels in the past isn't applicable - hope you get it sorted! And if you're ever travelling on the hume through or near albury I'll happily scan it for you with VCDS.