Many buyers find buying a used car stressful, with a key pain point being uncertainty about that car’s history. Was it used as a taxi? Well taken care of? Maintained properly?
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Understanding the basic main components of a car or truck, and the different variations and needs of those components, can help used car buyers avoid some uncertainty.
Next, we cover another important component of the new ride you’re considering: its ignition system.
Ignition systems come in many shapes and sizes depending on the age and make of used vehicle you are considering. Some work differently than others, but they all share the goal of sending electricity to spark plug electrodes inside the engine, which ultimately ignite the air-fuel mixture.
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Each cylinder in your gasoline engine has a spark plug threaded precisely into the cylinder head above. Some engines have two spark plugs per cylinder, but this is rare.
The spark plug slides into the cylinder, sealing out combustion gases and heat, while placing the electrode tip inside the cylinder for optimal combustion. The other end of the plug is connected to an electrical source (a large coil pack or a small ignition wire), which sends just the right amount of electricity to the plug at the right time to make it spark.
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A properly functioning ignition system has a lot to do with the performance, efficiency and refinement of your ride. This is the basis of life inside your car’s engine.
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Fortunately for used car buyers, ignition problems can be easily revealed and many common problems can be identified quickly if you know where and how to look.
Buyers looking for maximum confidence in their next used car purchase may find the cost of an ignition system overhaul minor compared to the peace of mind that comes with a known, healthy system.
Care of the spark plug
Spark plugs are like belts, filters and brake pads: they require regular replacement at predetermined intervals. These vary according to the age and type of vehicle, with many modern cars going 100,000 kilometers or more before requiring any attention.
Older cars, specialized performance models and turbo engines may have more frequent spark plug change requirements, perhaps every 50,000 kilometers. Hybrid car engines also have spark plugs. Diesels don’t.
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To find out how often spark plugs should be changed in the used car or truck you’re considering, check your owner’s manual or online at a maintenance schedule accessed through the manufacturer’s website. Be sure to enter the specific year, make, model, and engine you’re considering to get the correct figure.
Like engine oil, some drivers prefer to change spark plugs early, speeding up the intervals listed in the owner’s manual. That way, they choose to spend a few extra dollars on preventative maintenance and peace of mind. Others don’t.
Speeding up your spark plug change intervals may not harm your engine, and is a good idea if your engine will frequently see severe use such as extreme cold, non-stop driving, or a variety of other very hard driving conditions. canadian women
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If you are a Canadian buying a used car with more than 50,000 kilometers and the service history of that used car is unclear, budgeting for a spark plug change and ignition system overhaul along with your purchase is a great way to make sure you’re starting your ownership experience with confidence and reliability.
Can you change your own spark plugs?
Yes, but you probably shouldn’t.
Changing the spark plugs in some vehicles is quick and easy. Changing the spark plugs in others requires the removal of body parts or wheels, specialized equipment and special training.
To be clear, some vehicles are excellent candidates for a low-cost DIY spark plug change, as long as you know exactly what you’re doing and have the necessary tools and knowledge.
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If not, many things can go wrong. If the plug size, type, spacing, or installation torque is incorrect, you could cause serious damage to your engine that is not covered by the remaining warranty. Ditto if you disconnect the car battery incorrectly (or don’t).
A lot can go wrong when it comes to selecting and installing spark plugs in a modern engine, and there is no room for error. Leaving this job to the professionals means you’re off the hook if something goes wrong.
Spark plugs and direct injection (DI) turbo engines.
Many modern engines use direct injection (DI) technology, supercharging, or both.
In a DI engine, the intake valves are only used to control the flow of air into the cylinder while the fuel is poured directly inside at extreme pressure.
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In a turbocharged engine, the exhaust gases drive an air compressor that throws extra air into the engine, allowing it to burn more gasoline and produce more power. Most modern engines have at least one of these characteristics, and many have both.
High efficiency engines like these depend on a clean and precise combustion process to do their job properly. They are also sometimes prone to the buildup of “valve grime,” a contaminant that can build up in DI engines (turbocharged or not) over time.
Keeping the ignition system in this type of engine healthy is a very good idea. When used in conjunction with timely oil changes and high quality fuel, fresh spark plugs help form the foundation of the clean combustion process required to keep valve fouling and other deposits at bay.
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Starting your used car ownership experience with a new set of spark plugs and speeding up your spark plug change intervals is a good idea for any car or truck, and an even better idea if it has an engine installed. DI or DI turbo.
Pull the plug tubes
Depending on the used vehicle you are considering, it may be easy to remove the hood and remove the spark plug tubes. These are basically rubber-insulated electrical connectors that slide into the cylinder head and fit into the spark plugs below.
With this setup, the tubes can be removed by hand for inspection. In other configurations, the coil packs may be clamped to the top of the spark plug tubes, requiring the removal of a few fasteners to free each one.
Either on your own or with the help of a professional, removing these tubes can be a useful check for potential problems.
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When you remove the tube, listen carefully for a good suction sound of fluid. Look down into the opening, which should be dry, clean, and have a spark plug screwed into the bottom. If you see fluids, debris, and (especially) engine oil in one or more of these openings, the vehicle requires professional attention and repair before you buy, likely replacing a valve cover gasket.
Some engines (V6, V8, H4, H6) have multiple valve cover gaskets.
With the spark plug tube/ignition coil pack removed, the electrical wiring, contacts and insulation can also be checked for damage.
Burning, melting or cracking of the rubber insulation indicates a problem that can cost you money and create a bad driving experience. Spark plug wires that have been exposed to oil (such as a leak found in the previous step) can also be damaged.
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Replacing damaged or deteriorated ignition components is a great way to make sure your engine doesn’t suddenly die (or run like it’s about to) when you least expect it.
If you’re considering this check but aren’t sure whether or how to do it yourself, have a licensed technician do it for you. It will cost you a few dollars, but could save you hundreds or more.
What happens if you don’t change the spark plugs?
What if you buy a high mileage used car that has never had the plugs changed and then don’t bother changing the plugs?
Probably not good for your wallet.
In addition to missing the opportunity to inspect wires, coil packs, and plug tubes for signs of trouble and damage, old spark plugs tend to degrade and dirty quickly once they’re past their prime. , making it increasingly difficult for your engine to start. air-fuel mixture efficiently. This can lead to poor performance, misfires, carbon buildup, incomplete combustion, a check engine light (CEL), and accelerated wear of other ignition components.
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Old plugs can also cause collateral damage to other parts of the engine, increasing repair bills. As combustion becomes less efficient, it becomes dirtier. This can lead to an accelerated build-up of dirt and deposits inside the engine. This further contributes to dirtying your sloppy plugs.
If a spark plug completely loses its ability to fire, the engine will run very poorly, waste a lot of fuel, wear out quickly, and can even damage your expensive catalytic converter.
Old plugs can physically fail, dropping bits or pieces of weathered metal into the engine cylinders. The offending metal debris then chews into the cylinder walls and will damage the pistons and valves, causing permanent and potentially fatal engine damage.
It is much cheaper to change a set of plugs than to change an engine.
