Engine Vibration vs. Drivetrain Vibration
Not all vibration in a car comes from the engine. Vibration that's felt through the steering wheel tends to come from the front wheels or tyres. Vibration through the seat and floor at highway speeds can be tyre balance, prop shaft balance, or wheel bearing. Vibration that follows engine RPM (not speed) and is present even when the car is stationary in gear points to the engine itself.
This guide focuses on engine-originated vibration.
Engine Misfires
A misfiring cylinder is the most common cause of sudden engine vibration. Each cylinder fires in sequence — if one doesn't fire (due to a faulty spark plug, ignition coil, or injector), the rotational force from that cylinder is missing. The engine runs unevenly, causing a rhythmic vibration that is felt and heard.
Misfire vibration is typically felt through the whole car, is worse at idle, and often comes with a check engine light showing a misfire code.
Engine Mounts
Failed or collapsed engine mounts allow the engine to move excessively within the engine bay. Every combustion pulse and deceleration event causes the engine to rock further than it should, transmitting vibration directly to the chassis and body. Engine mount vibration is typically felt most during gear changes, throttle application, or when the AC is switched on (adding compressor load).
Engine mount replacement: $150–$500 NZD per mount, fitted.
Idle Air Control / Rough Idle
A rough, fluctuating idle can cause the whole car to shake noticeably, particularly in older vehicles with softer engine mounts. The engine RPM cycles up and down if the idle speed controller is malfunctioning, creating a rhythmic vibration.
Timing Issues
An engine with incorrect ignition timing (too retarded or advanced) or a timing chain that has jumped a tooth will run unevenly, causing vibration alongside poor power and potential misfiring.
Harmonic Balancer Failure
The harmonic balancer (crankshaft damper) on the front of the crankshaft absorbs rotational vibration. When its rubber component separates or degrades, rotational vibration passes into the engine and ancillaries. Severe balancer failure causes dramatic vibration at all RPMs and can damage front engine seals and accessories.
Replacement: $200–$500 NZD fitted.
When Vibration Is an Emergency
Sudden, severe vibration from the engine area that appears without warning — especially if accompanied by knocking or a loss of power — could indicate a catastrophic internal failure. Don't continue driving; pull over safely and investigate.