Ask a mechanic - 11/04/07

A: You haven't told us what type of car it is, but what you describe is typical of the engine having burnt-out or stuck-open valves. These would prevent smooth idling and would certainly result in unburned petrol coming through the exhaust. Get a cylinder compression test done.

ALL FLOPPY IN THE HAND
Q: I was driving along recently, and when I went to change gear the gear lever went loose and sloppy in my hand, and hasn't worked since - I had to be towed home. What has happened? Posted by: claphen1

A: It's hard to be precise without knowing the car type, but it sounds as if a ball joint in the external gear selector mechanism has popped apart. This can sometimes happen on some front-wheel drive cars. Failing that, it must be an internal gearbox failure.

TOO ENERGETIC BY FAR
Q: I have a 1999 VW Polo 1.6. Every time I start the engine, it revs itself unaided up to a frightening-sounding 4000rpm or so. It does settle down some time later but I'm worried it will damage itself and would like to know how to cure this problem. Posted by: irresponsible_biker

A: This is a fault with the injection system's fast-idle circuit, which is over-supplying the engine with fuel and air, possibly because it's receiving duff information from a faulty engine sensor. Take the car to a VW dealer or injection specialist and ask for a fault-code check.

A COSTLY BUNCH OF BALONEY
Q: My Vauxhall Zafira's central locking has packed up. When I push the remote button the lights flash and the boot lock opens, but the door locks don't unlock - they have to be opened manually. My Vauxhall dealer reckons the car has to be "re-loomed" at a cost of £800! Posted by: pdiane91

A: That sounds like a load of baloney. It's much more likely to be a fault with the master lock solenoid, with a system electrical connector, or with the central locking control unit. We can see no reason to assume it needs a new loom. Get an independent auto-electrician onto it.

DRIVING MY HONDA IS A GRIND
Q: I get a grinding noise from my 1997 Honda Civic when it's in any gear, including neutral at higher revs, and the noise is getting louder. But if I select neutral or press-in the clutch when driving at speed, the grinding noise disappears. Any idea why? Posted by: ruslabon_99

A: Is the grinding noise related to road speed or engine speed? If the former, we would suspect failure of a gearbox or final-drive shaft bearing, but if the latter, you might be looking instead at a problem with the gearbox input shaft, or with the clutch release bearing.

TRAILS IN THE DUST
Q: I own a T-plate Renault Megane Coupe. Whenever it rains, the passenger side fills with water, yet when hose-water is fired over the car, none of it gets in. I have been advised that this might be due to a windscreen leak around the edges, but I don't know. Posted by: hitmeup2047

A: This is probably only happening when you drive the car at speed because this creates a low pressure - effectively a vacuum - within the cabin, drawing the water in. If possible, strip back the carpeting in the affected area, dry it, sprinkle it evenly with talcum powder, then take the car for a wet-weather drive. You should then be able to see trails of water in the powder, leading you to the point of entry.

GO FOR THE DIESEL INSTEAD
Q: I am all set to buy a used Land Rover Freelander 2.5V6 for £3,500, but after reading some articles about this model I'm not so sure now - it seems that 1.8 models are preferred - would you buy one? Posted by: miketierney

A: This is subjective, but we would choose the diesel version over the other two. The 1.8 is a bit weak, the V6 is horribly thirsty, but the 2-litre turbodiesel is punchy, refined and very frugal. It would be our choice.

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