How do I know if my car's engine is misfiring?

By Julia Freeman

One problem that is more common than you may think with a modern internal combustion engine is that of misfires. The spark plugs within an engine provide an arc of electricity which ignites the fuel, enabling the cylinders to fire and the engine to operate effectively.

Car Engine

There are many aspects that can cause a misfire, which our years of experience tell us can be confusing unless you know what to look for. This short guide can assist you in troubleshooting a misfire, helping you to diagnose the issue in order that it can be repaired quickly.

Acceleration or idle is rough

If a car engine is misfiring, it is often felt when accelerating under certain conditions. If acceleration is taking place with the rev counter on the higher side and the engine in higher gears, a jerk coming from the engine is indicative of a misfiring engine. Similarly, if when an engine is idling, it sounds and feels uneven or rough you are likely to be experiencing a misfire.
Vibrations occurring through the cabin when accelerating or idling are also indicative of an engine misfire. When car engines are manufactured, they are designed to be balanced, and misfiring engines can throw off this balance, causing vibrations.

Check Engine Light is on

As you may expect, the check engine light is definitely indicative of a problem. The details from issues within an engine are analysed by the onboard control unit and if this happens several times, or the control unit deems the issue serious enough, the display will light up. The biggest takeaway here is not to ignore the light!
The causes can vary, and a good mechanic can diagnose and address these in short order.

Bad ignition coil on an older vehicle

Right at the top of the list of culprits for a misfiring engine is the ignition coil. Ignition coils were fitted in conjunction with a distributor in conventional non-electronic ignition systems. In order to diagnose and fix this issue, each coil can be unplugged, to ascertain whether or not cylinders are responding. This helps to identify any spark plugs or ignition coils that need to be replaced.

Worn spark plugs

Up next is a bad spark plug. Generally speaking, very cheap and easy to replace, if you have no idea when the spark plugs were replaced on your engine, it is likely to be time for some new ones.

Gasket leaks

If your intake manifold gasket is not fully airtight, it can cause issues with the engine firing effectively. This is far more common in an older engine, due to the prevalence today of steel gaskets. Any leaks around the engine, however, including vacuum hoses can cause a misfire.
If you are concerned about any performance issues with your engine, why not book an appointment at your local Protyre garage and have our experienced mechanics take a look at your issue. We also stock tyres at highly competitive prices from leading brands including Bridgestone and Pirelli, should you require replacements.

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About the author

Article Author Photo
By Julia Freeman
Julia is Head of Brand Marketing for Micheldever Group and loves engaging with customers and the business as a whole to deliver their automotive needs.
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