Alex Robbins is contributing editor at Telegraph Cars where, as well as responding to readers’ queries, he also contributes reviews of new and used cars, together with articles on buying and selling. 

His knowledge of the used car market informs his many buying guides relating to the best buys in particular sectors, with an emphasis on value for money.  Every week he will answer your questions on buying and selling, as well as solving your car problems, whether consumer or mechanical.

Do you have a motoring dilemma you’d like our expert to solve?  For consumer and used car advice, or car faults, email CarsAdvice@telegraph.co.uk and include your subscriber number. This week’s question… 

Dear Alex,

I have a 2015 Hyundai i10 which has an engine warning light appearing, indicating a cam timing fault, with reduced acceleration. My garage checked the timing chain tensioners, did a full service using a high grade oil and replaced the cam sensor with a Hyundai part. The warning light has come on, gone off, and then come on again since. The engine is not making any noises and when the warning light is off the car drives perfectly. The garage, albeit reluctantly, has booked it in to change the timing chain. Is this the right move, or should I take the car to a Hyundai dealer for a diagnostic check instead? 

– CG

Dear GS,

The timing chain is a pretty big job, even on a car as small as the i10, so I’m not sure I’d go to the extent of doing that at this stage, partly because there are cheaper causes of this issue that should probably be ruled out first. It would be extremely upsetting to spend a fortune changing the timing chain only to discover the problem persisted.

As it happens, this sort of issue is not unknown in modern Hyundai engines, though it is uncommon. Usually, it indicates a problem with the variable valve timing system, which is governed by an oil control valve; essentially, when instructed to do so by the control unit, this little gizmo allows oil into the variable valve timing system, which uses hydraulics to adjust the timing as you’re driving.

Sometimes, however, the oil control valve gunks up, so it can’t open and close properly. This affects the correct operation of the variable valve timing system, meaning that at certain points your engine isn’t quite timed properly. The resulting discrepancy in readings from your car’s cam timing sensor is then picked up by the car’s control unit, which characterises it as a failure of the cam timing system. 

Your local garage should be able to remove the oil control valve relatively easily (it’s near the top of the engine) and test it using a 12V feed. If it does prove to be at fault, they can try cleaning it using some carb cleaner, which might mean you don’t need to even buy a new part – or, if not, they can always replace it with a new one from Hyundai.