A recent Mazda CX-5 rolled into our Perth workshop feeling sluggish, hesitant off the line, and generally a bit sorry for itself. ⚡ One quick inspection later, and the culprit was staring right back at us: a set of spark plugs that had well and truly clocked out. Swapping them for fresh units transformed the way the car ran, and it’s a perfect reminder of just how much these small components influence engine performance. 🔧
What Spark Plugs Actually Do (And Why They Wear Out)
Spark plugs are responsible for igniting the air-fuel mixture inside each cylinder. Every time your engine fires, a precisely timed electrical arc jumps across the plug’s electrode gap to start combustion. Multiply that by thousands of ignitions per minute, and it’s easy to see why plugs eventually degrade.
Over time, the electrodes erode, carbon deposits build up, and the gap widens beyond spec. The result? A weaker, less consistent spark that struggles to ignite the mixture cleanly, exactly what we found in this CX-5.
The Symptoms of Tired Plugs
When spark plugs are on their way out, your engine will usually tell you. Common warning signs include:
- Rough or hesitant idle caused by inconsistent combustion across cylinders
- Reduced fuel economy as unburnt fuel is wasted
- Misfires that trigger a check-engine light or noticeable stumbling under load
- Harder cold starts and slower throttle response
- Loss of power, particularly during acceleration or hill climbs
Left too long, worn plugs can also put extra strain on your ignition coils and catalytic converter, turning a simple service item into a much more expensive repair.
Getting the Replacement Right
Spark plug replacement isn’t just about pulling the old ones out and threading new ones in. Correct plug specification, gap setting, torque values, and even the anti-seize application all matter, particularly on modern engines with aluminium heads. Using the wrong heat range or an incorrectly gapped plug can cause pre-ignition, poor running, or thread damage that turns a routine job into a nightmare.
For most petrol vehicles, manufacturers recommend replacement between 40,000 and 100,000 km depending on the plug type. If it’s been a while, or you’re noticing any of the symptoms above, it’s worth booking a check.
If your car’s feeling flat, drinking more fuel than it should, or just isn’t running the way it used to, the team at Romano’s Automotive in Perth can diagnose the issue and get you back on the road running smoothly. Book your service online at https://shopcommand.com.au/book/romanos-automotive or give us a call on 0401 747 320 or text 0482 074 129.
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