Why does our Volkswagen Polo diesel hold its revs when I lift my foot off the accelerator?

In January this year we bought a new 3-door Polo SEL 1.6 TDI, downsizing from our long-lived, and immensely practical, Saab. In most respects the Polo fits our present needs very well indeed and we have no regrets - except for two potentially dangerous conditions.

The first is an embarrassing tendency to stall in first gear unless one is very careful to keep the revs up. The Volkswagen dealer checked engine mapping at the initial service and said it was correct. The other problem occurs spasmodically. Lifting off the accelerator pedal normally produces an anticipated immediate drop in revs, but not ALWAYS. There can be a marked delay. Interestingly our daughter bought a Polo Moda 1.2 at the same time and has no problems at all.

Asked on 15 December 2010 by JB, Trelleck, Monmouthshire

Answered by Honest John
This could be deliberate because it has been discovered in London taxis that setting off from engine idle speed in a diesel shortens the life of its dual mass flywheel. Setting off with some revs is much kinder to the DMF. That said, the 1.2TSI 105 and 1.4TSI 122 petrol engines are nicer to drive and potentially more reliable.

With a modern diesel, at between three and six years old, you risk: new diesel particulate filter (£500 - £1,000), new dual mass flywheel and clutch (£900 - £1,200), new EGR valve (£500 - £750) and new turbo (£1,000 - £1,500). Once the public cottons on to these costs, I predict that enthusiasm for diesels will wane, residual values of 3-year-old diesels will fall and leasing costs of diesels will rise.
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