It’s very likely to be a sensor problem. If the sensor in question starts to send false information to the car’s computer, the engine can do all sort of weird things. I’ve even heard of things like exhaust gas temperature senders on this make and model being mixed up during a DPF service with all sorts of problems as a result.

Beyond that a high idle can be the result of a fuel injector problem or even a vacuum leak through a split or missing rubber hose. Even the turbocharger’s trunking – if it becomes split or damaged – can cause this sort of problem, but usually the drama would be a permanent one until the problem was fixed. The intermittent nature of your problem has computer or sensor written all over it. A full electronic scan of the vehicle should be your first step. There’s a very good chance the onboard computer already has a pretty good idea of what’s wrong. You just need to ask it.

The VW 1.4 TSI engine uses a cam-chain rather than a rubber toothed belt which needs periodic replacement. As such, the cam-chain should last the life of the engine (and the rest of the car) but experience with this engine suggests that is not always the case and some early versions of this engine have required cam-chain replacement. The incidence of this seems a bit random, with no real pattern emerging with some cars going on to record normal mileages with no cam-chain problems.

The car you’re looking at, however, is a later version, so should be less prone to this. But even so, make sure the car has a perfect service record as poor maintenance can shorten the life of the cam-chain.

From the sounds of things, you need a vehicle that can accommodate the wheelchair as an actual seat in the car rather than having the chair folded and stored for the journey. With that in mind, a van or people-mover is by far the best best bet and the news is good, because there are plenty of choices. For a while there, people were converting Ford Falcon station-wagons for this task, but since the Falcon is no longer made, vans have become the new default vehicle to convert. Which makes plenty of sense.

There are specialist firms around that will carry out whatever conversion you require and tailor-make the ramps, lock-down points and grab-rails you need to make it work for you. Switched on companies will sit down with you and discuss your precise requirements and engineer something bespoke if necessary.

At the moment, the list of car choices is pretty long and includes the new Hyundai Staria, VW Caddy, LDV G10, VW Caravelle, Renault Kangoo, Renault Trafic, Hyundai iLoad, Mercedes-Benz V-Class, Toyota HiAce and, in case you need something really big, even the Toyota Coaster. Some of these companies are also registered as NDIS suppliers.

But don’t rule out a second-hand vehicle, either. There are websites around listing used wheelchair-accessible cars for sale. Some will be ex-taxis, but others can be relatively low-kilometre cars that might just have the exact layout you were looking for.