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Automotive glossary

Spark Plug Gap

The spark plug gap is the distance between the centre and ground electrodes.

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What is Spark Plug Gap?

It affects spark strength and ignition reliability. Manufacturers specify the gap. Many modern plugs are pre-gapped. Checking the gap with a wire gauge is more accurate than a flat feeler gauge on worn electrodes. Engines with high boost pressure often need smaller gaps. Plugs that have been dropped can have a changed gap or cracked insulator.

How it works

The spark jumps across the gap to ignite the mixture.

Why it matters for your car

A wrong gap can cause misfires. Iridium and platinum tips can be damaged when adjusting.

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