What causes spark plugs to fail? | AutoGuru
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What causes spark plugs to fail?

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Updated 10 Oct 2019

Zak Zuiderduin

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What does the spark plug do?

Spark plugs in your engine ignite the air fuel mixture in the combustion chamber, giving energy to the pistons which are forced downwards, which then moves the crankshaft which then . . . you get the picture – spark plugs are the piece of kit that give your car’s engine the ‘spark’ it needs to get moving.

Your vehicle’s manufacturer will specify a particular spark plug to suit your car’s engine.

Those specifications will include the spark plug type (conventional, platinum, Iridium) a heat range that the spark plug operates at, what thread type, the reach/length of that spark plug, and the spark plug gap (the clearance between the centre electrode and the ground electrode).

If you get any of that wrong, your spark plug will fail, and you can cause serious engine damage.

It’s always best to follow the manufacturer’s guidelines.

What about fitment?

What a lot of people don’t realise is that the spark plug must dissipate its heat via the cylinder head.

Given this fact, it is important that the spark plug be torqued to the correct tension using a torque wrench.

An under-torqued spark plug will not dissipate the heat correctly which can lead to detonation or pinging, causing engine damage.

An over-tightened spark plug will stress the threads which can damage the cylinder head and the spark plug itself.

Anything else?

Of course there is.

If the engine isn’t tuned correctly, uses low grade or dirty fuel, is overheating . . . all can cause spark plug problems.

So, if you feel any sort of engine hesitation, misfire or rough running, take your car to a professional mechanic on AutoGuru and have it looked at, before it causes an expensive failure.

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Written By

Zak Zuiderduin

Zak has been working in the auto industry for 40 years.

For the past decade, he has been in the education business, training apprentices and preparing them for a career in the light vehicle and auto electrical trades.