Engine Misfire or Juddering? Common Causes Explained

18 June 2026 · 6 min read

What a misfire actually is

A misfire is when one or more cylinders fails to burn its fuel and air properly. You feel it as a judder or shake, especially at idle or under load, often with a loss of power, poor economy, and the engine warning light. A misfire bad enough to risk damage will make the engine light flash rather than stay on.

For an engine to run smoothly it needs a good spark, the right amount of fuel, and proper compression in each cylinder. A misfire means one of those three is missing somewhere, and the job is to find which.

Common causes

On petrol engines the most common causes are worn spark plugs and failing ignition coils, which stop a cylinder firing cleanly. A blocked or leaking fuel injector, a vacuum leak, or a faulty sensor feeding the management system can also cause it.

On diesels a misfire more often traces to injectors, compression problems, or glow plug and fuel system faults. On any engine, a fault code stored in the management system usually points us to the cylinder involved, which speeds up the diagnosis.

Why not to ignore it

A persistent misfire is not just uncomfortable — unburnt fuel passing into the exhaust can overheat and damage the catalytic converter, which is an expensive part to replace. A flashing engine light in particular means you should ease off and get it looked at promptly.

The good news is that many misfires come down to relatively inexpensive parts like plugs or a coil, and fixing them early restores smooth running and economy while avoiding the bigger bills.

Misfire diagnosis in Bilston

If your engine is juddering, down on power, or showing a flashing light, we will read the fault codes, test the ignition and fuel systems, and pin down the cause before advising — so you only pay for the part that is actually at fault.

Call Wolverhampton Auto Care on 01902 494948 or book online. We are on Hare Street, Bilston, WV14 7JW, serving Darlaston, Willenhall, Wednesbury and Wolverhampton.

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Need help with your car?

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Call 01902 494948