Q My new Vauxhall Corsa 1.2 has electronic throttle control, which tends to rev the engine when I change gear. My dealer has checked the software and says there is no problem, but it is annoying. Is there a way to fix it? - JS from Glasgow

A The technology is trying to make gearchanges easier, which may be helpful for learner drivers. By detecting when the clutch is depressed and increasing the revs slightly - especially when downshifting – it is trying to prevent possible stalling or rough take-up on the gearchange.

However, if you still think it’s a fault and the dealer insists it’s okay, why not test a similar vehicle from the forecourt, which will confirm if it is a feature of your car?

Q I have a Jaguar S-type R, which I bought from a franchised dealer in Manchester. The car is due for its first service next month and the dealer tells me it will lose its warranty if I have it serviced with another garage. Is this true? I could save a lot of money by going to my local garage. - NC from Altrincham, Cheshire

A To maintain the warranty you must have your Jaguar serviced and/or repaired by a Jaguar-approved service centre - a handful of these are nonfranchised garages. For a full list of authorised repairers go to tinyurl.com/5qwz76 and where it says “select dealer type”, chose authorised repairer. The UK has 95 Jaguar franchised dealers, plus eight authorised repairers.

Q We recently replaced our Peugeot 406 coupé with a Peugeot 407 SW diesel to accommodate our two grandchildren and three dogs. The 407 suffers from squealing brakes and two trips to the garage have failed to cure them. My dealer now says it is a feature of the car. Can that be right? - TM from Farnborough, Hampshire

A The squeal is caused by the brake pads vibrating at high frequency against the brake discs. This problem does not affect brake operation. It occurs because the leading edge of the pads “bites” into the disc, causing the pads to vibrate. Manufacturers try to overcome this by damping the vibration with springs, shims (packing pieces) and cushioned pad backings.

If yours are making a noise then some of these springs and shims might need lubrication. A copper-loaded brake grease on the backs of the pads may help solve the problem. We suggest you try a different dealer if your original one has been reluctant to help.

Q I have a motorhome on a Ford Transit chassis. Next year I want to use it to tow a small car to France. The motorhome can pull weights of up to 1,200kg. Can you recommend the lightest, secondhand, four-door car, under 1000cc, that could carry two adults and two children on holiday while doubling up to do a short school run during the year? - WT from Wexford, Ireland

A The most obvious suggestions are the Citroën C1, Peugeot 107 and Toyota Aygo, which share common underpinnings. They all weigh less than 900kg and are available with five doors. Also consider the five-door Daihatsu Sirion 1.0 S at 890kg and, at a push on weight, the Kia Picanto 1.0 at 1,005kg looks great value both new and secondhand.

A slightly unusual suggestion would be the 1 litre Opel/Vauxhall Agila. This is considered a mini MPV but weighs just 975kg and offers excellent interior space.

My boyfriend and I own a K-reg Mercedes 190E, which is used mainly for short town journeys of five miles or less. He insists on warming up the car before every journey by letting the engine idle for 10-15 minutes, then revving it. He says this is necessary to keep a car of this age in good running order, but I consider it to be a waste of petrol. What is your view? - LF from north London

A Though well intentioned, your boyfriend is wasting money and creating unnecessary pollution into the bargain. Letting the engine idle for 30-60 seconds is about right, as this will give the oil a chance to work its way around the engine. After this, it’s advisable to keep the revs down until the engine is up to operating temperature.

It’s also a good idea to always reverse into a garage or parking area, as driving off forwards is more fuel-efficient than manoeuvring the car onto the road in reverse with a cold engine. And, by the way, if your car is unattended during your boyfriend’s warm-up routine and is stolen by an opportunistic thief, your insurer is unlikely to pay out.

Q I am looking for an executive sports car with a tailgate and a boot big enough for a labrador dog. I like the Jaguar XKR but the boot will not take a dog and the back seat isn’t big enough. I like the Audi A5, but it doesn’t allow entry to the boot from inside the car. Is there a suitable car that combines the advantages of both the Jag and the Audi? - JL from Tiverton, Devon

A You have described the logic behind the Reliant Scimitar, a sporty two-door estate that originally attracted well-heeled country-set owners (Princess Anne was one) partly because it had enough room in the back to carry gun dogs to and from a shoot at speed.

Neither the Scimitar nor a direct replacement is now produced because most owners prefer four doors on their estate cars. However, there is a good choice of high-performance four-door estates that should suit your requirements. Take a look at the BMW M5 Touring (£68,495), Audi RS 6 Avant (£77,730) or Mercedes-Benz E 63 AMG (£69,880). All will keep up with the Jaguar XKR.

Q In the past two years the glass on my four-year-old Vauxhall Corsa has developed a patchy smearing, which shows up only in rain and makes visibility dangerously poor, especially at night. I have tried cleaning the glass with conventional glass cleaner, white spirit and special car glass polish, but the smears remain. What can I do? AP from Brighton

A You could try cleaning it again using a weak mixture of warm water and washing-up liquid, which is good at cutting through grease. (It should not be used on the bodywork as it contains salt, which can remove protective wax polish.)

Whatever happens, don’t be tempted to attack the screen with anything harsh (kitchen scourer, wire wool etc) as this will damage it beyond repair.

It could also be that it’s time to change your wiper blades. As they get older, they deteriorate, which sometimes results in the kind of smearing you describe. They may look fine to the naked eye, but blades are best changed once a year - just before the MoT is the best time.

Blades from Valeo, Champion and Bosch do well in independent testing; you can find them in most car parts stores.

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E-MAIL YOUR QUESTIONS TO carclinic@sunday-times.co.uk . Alternatively, write to Car Clinic, InGear, The Sunday Times, 1 Pennington Street, London E98 1ST. Please supply us with a daytime telephone number, the town or city you live in and as much detail about your car as you can. We regret that we cannot send personal replies or deal with every letter, so please do not send original documents or SAEs. Advice is offered without legal responsibility