Engine · Symptom guide

Engine Misfiring or Shaking: Causes and Solutions

In short: an engine that misfires or runs roughly is most often suffering from an ignition fault (spark plug, coil) on a petrol engine, or a faulty injector. Worn engine mounts can also cause vibration without any misfire. Low compression on one cylinder is less common. If the engine warning light is flashing, reduce speed immediately: the catalytic converter is at risk.

Main causeIgnition or injector

UrgencyHave it checked soon

Can you drive?Over a short distance

SolutionSpark plug, coil or injector

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Shaking or Misfiring: What You're Experiencing

The engine shakes at idle, the car "splutters" under acceleration, or the engine warning light comes on — sometimes flashing. These symptoms most commonly point to a cylinder that isn't working properly: it's no longer producing its share of power, causing an imbalance.

Likely Causes

Ignition (petrol engines): worn spark plug, faulty ignition coil. A very common cause and an inexpensive fix.
Injector clogged or faulty, petrol or diesel.
Air leak on the intake.
Worn engine mounts: the engine shakes without misfiring, especially in D on an automatic.
Low compression on one cylinder: valve, piston rings or head gasket.

Flashing engine warning light: reduce your speed and have the car checked without delay. Unburnt fuel is reaching the catalytic converter and can destroy it.

How the Garage Identifies the Faulty Cylinder

Reading the fault codes often pinpoints the cylinder involved. The mechanic then swaps the coil or injector with a neighbouring cylinder: if the misfire follows the part, that part is the culprit. If it stays on the same cylinder, a compression test is carried out to assess the engine.

Can You Keep Driving?

Over a short distance, without pushing the engine. A persistent misfire overloads the other cylinders, damages the catalytic converter and can dilute the oil with fuel.

Repair or Replace?

Spark plugs, coils and injectors are straightforward to replace. Only confirmed low compression (burnt valve, piston rings, head gasket) implicates the engine itself. In that case, a reconditioned engine sold on an exchange basis, supplied as a bare engine and warranted for up to 24 months, may prove more cost-effective than a major repair.

The EDEN BOITES solution

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Reconditioned part on an exchange basis, bench-tested, with up to 24 months’ warranty, payable in 10 instalments. Your vehicle details are all we need to find the right reference.

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Frequently asked questions

When cold, the mixture is richer and components are more sensitive: a worn spark plug or injector tends to show up first at this point. If the misfire disappears once the engine is warm, it is a sign of early wear and should be investigated.

No: worn engine mounts transmit vibrations without any misfire at all. If the engine warning light stays off and the vibration increases when selecting D or reverse, think engine mounts.

Other symptoms

Diesel power loss or limp mode Blown head gasket: the symptoms All symptoms: full diagnosis

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