Although Saab GB claims its retail network has "more than adequate stocks" a spokeswoman admits: "There has been some feedback from a few customers about urban stop-start driveability. This is a fairly new engine and we want to get it 100 per cent right."

The source of the problem is a vibration from the 3.0-litre, common-rail Isuzu power unit's turbocharger which generates a resonance amplified through the Saab's subframe.

Engineers developing the Vauxhall Signum and Vectra models, due to use the same engine later this year, are co-operating with Saab counterparts after countering what one technician described as "vibration and buzzing" by tuning hydraulic engine mountings.

The V6 TiD accounts for around 10 per cent of 9-5 sales, with about half going to the corporate fleet business. Linear, Arc and Vector model derivatives with the V6 diesel had prices slashed by £1400 in October last year. Saab dressed the cuts as an initiative to help reduce company car tax liability.