What spark plugs can tell you about your engine


Have you ever had problems with your engine’s performance? Completely rebuilding or buying an engine can cost upwards of $4,000 – $8,000. That’s a lot of money! What can you do to keep an eye out for engine problems so you don’t end up having to pay a fortune for a new engine? Believe it or not, your spark plugs can be a great place to start looking for engine problems.

What can a spark plug tell you? A spark plug – in particular the area around the electrodes – can give you insight into your car’s condition. You can even learn how to “read” spark plugs. Here are a few things to look for:

Spark plug with ash deposits

Spark plug with ash deposits

The head of the spark plug is a red rust color – Your fuel additive is probably not quite right. If you are adding a fuel product such as STP fuel additive then your vehicle is fine. However, if you are just buying your fuel straight from the gas station and you see this red color, you should probably get your fuel somewhere else.

Spark plug with fuel deposit

Spark plug with fuel deposit

The plug has fuel on the top of it – You are probably burning an overly rich mixture of fuel in your vehicle, using a dirty air filter, or idling for a long time. You may need to set the choke differently.

Spark plug with oil deposit

Spark plug with oil deposit

The spark plug has oil all over it – You probably have an oil problem and need to get the rest of your engine looked at, since oil may be leaking into the combustion chamber. You’ll also need to clean and regap the plug.

Spark plug with sandy-textured deposit

Spark plug with sandy-textured deposit

The spark plug has a heavy deposit with a light gray, sandy texture – This is often the result of a worn valve guide, excessive use of upper cylinder lubricants, or idling for long periods of time.

Spark plug with burned electrode

Spark plug with burned electrode

The electrode has been burned away or damaged – This is probably a pre-ignition problem and the timing need to be changed. You might also check the plug temperature valve, gap width, and lean fuel/air mixture. The spark plug will need to be replaced.

Worn spark plug

Worn spark plug

This is what your spark plugs should look like after being used!  – You’ll notice a grayish-tan or brown deposit on the electrode. Worn plugs need to be replaced.

As you can see, a spark plug is a huge tattle tell of your engine’s problems. When your engine isn’t functioning properly, make sure to check them out!

Tip: Only check one spark plug at a time, and don’t mix plugs in different stages of wear. So you should either clean and put back all the old plugs or replace all the plugs.

Cars are complex machines and can often be puzzling. That’s why we’re here to help! Contact us at our website or drop by our shop – we’ll be happy to answer your questions!


~ by 2ndtononeservice on August 16, 2013.

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