Q1: My 2013 Kia Optima K5 has clocked about 13,000km so far.



About two weeks ago, I started to notice a faint noise (tak-tak-tak) coming from the engine bay when the engine is idling.



When I opened the bonnet, the engine was vibrating a wee bit excessively than I had expected when I first saw the car in the showroom.



I was planning to bring my car to the nearest service centre for a check-up but I wish to know what could spark this problem.



If you can tell me what the possible causes are, then I can direct the technician to check them as I don’t have much confidence with the service centre in my area.



Tay

Muar



The car is considered very new. The most probable cause of this noise is the idle speed controller, especially if the engine is vibrating at idle. Also check the engine and gearbox support including the mountings for any possible defects.





Q2: My 13-year-old Proton Iswara doesn’t seem to run well with RON95 petrol.



It’s emitting a lot of engine noise and is losing power and lacking acceleration compared to the period when I was filling it up with RON97 petrol.



The engine would also not stop immediately when I switched off the ignition.



KW Ma

Penang



What you have described appears to be signs of a serious engine problem. It seems that your engine is experiencing what we called “dieseling” – self-igniting even though the ignition  has been switched off. The cause of this problem is that there is a lot of carbon-build up inside your combustion chamber.



In order to eliminate this problem, you will need to remove the cylinders for inspection.



Did you alter the ignition timing? If yes, a too-advanced ignition timing will cause knocking and hence maybe the cause of ‘engine noises’ that you are hearing.



Get your engine checked by a trusted workshop so that you have a better idea about your complaints because there are many possible causes to this kind of problem.





Q3: I own a 14-year-old 1.6-litre Toyota Corolla SEG. 



In the past few months, the car has failed to start a few times.  The workshop mechanic has replaced the car’s starter.  However, till today, it still takes a few attempts (turning the key in the ignition) before the engine starts. 



How do I resolve this once and for all?



AG 

Petaling Jaya



There are many probable causes that may contribute to this kind of problem such as the ignition, fuel, electrical systems or even the battery itself.



Try to measure the battery voltage during cranking. You must get at least 9 volts; anything lower means it may be difficult for the engine to crank.



The issue could be a defective ignition switch and related components, loose electricals that is common even in new cars.



Your fuel pump might also be faulty or close to expiration.



Send your car to a workshop to narrow down the cause.