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2007 Ford Focus (Ford)

2007 Ford Focus


You & Your Car

Help! Why is my car’s engine knocking? Add to ...

I’m driving a 2006 Ford Focus 2.0Si. It’s got a knock in the engine as I’m driving. The more I accelerate, the more the noise in the engine. Do you know what could be the cause? Also note that there are oil leaks as well in the engine. – Bandile in Pietermaritzburg, KawaZulu-Natal, South Africa

I’m not familiar with your particular version of the Focus from South Africa – at that time Ford was producing different versions on different chassis with different engines in various parts of the world.

Having said that, your problem is pretty much universal. Engine knocking is generally related to improper combustion – the air/fuel mixture in the cylinders igniting prior to, or after the correct, moment in time.

The internal combustion gasoline engine depends on the air/fuel mixture being compressed as the piston moves up within the cylinder. At a very precise and pre-determined time, that mixture is ignited by a spark creating an explosion that forces the piston back down, turning the crank shaft and so on through to the drive wheels. If the mixture ignites for any other reason or at any other time the resulting explosion is heard as the sound you refer to.

The cause could vary from incorrect timing – the system has fallen out of tune causing the spark plug to fire at the wrong time. The cure could be as simple as having the timing checked and adjusted or as complex and expensive as a broken or badly worn timing belt.

If the timing is correct, another problem to look for is the quality of fuel you are using. If it contains too much sulphur or lead, it could be creating deposits within the combustion chamber or on the spark plugs.

The oil consumption might be related to premature wear caused by minute pieces of metal being dislodged by the uncontrolled detonation. Whatever the cause, the knocking can be a nasty piece of business, ultimately causing terminal engine failure – get it looked at as soon as possible. In the meantime, use the highest octane gasoline at the pump, avoid lugging the engine or using high revs.

Please send your automotive maintenance and repair questions to globedrive@globeandmail.com

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