Spark Plugs & Ignition Coils

Spark Plugs and Ignition Coils for Sale

This page lists the spark plugs and ignition coils we sell, along with diesel glow plugs. Every item above is in stock to order online, and each product page shows the part number, the pack size and the vehicles it was made for. If your engine is misfiring, idling rough, burning more fuel than it used to or setting a misfire code, this is usually the first place to look.

Most of the spark plugs here are iridium or platinum, sold in sets of 4, 6 or 8 so you can replace a full bank at once. The ignition coils include single coils, 4-coil packs and a 6-coil set for the Nissan GT-R. We also carry glow plugs for older diesel engines, because they do the same job of starting combustion, just in a different way.

Below you will find what each product is, how spark plugs and ignition coils work, how to tell which one is failing, how to pick the right part number, and a short set of answers to the questions people ask us most.

What We Sell in This Category

Here is the current range, grouped by type. Click any product name to see photos, the full fitment list and the price.

Iridium and Platinum Spark Plugs

Ignition Coils and Coil Packs

Diesel Glow Plugs

If you do not see your engine, check the brand pages such as Toyota parts, Nissan parts, Honda parts or Ford parts, or send us your part number and we will tell you if we can supply it.

How Spark Plugs and Ignition Coils Work Together

A petrol engine needs three things in each cylinder: air, fuel and a spark at the right moment. The spark plug supplies the spark. It screws into the cylinder head with its tip sitting inside the combustion chamber. When a high voltage pulse reaches the plug, it jumps the small gap between the centre electrode and the ground electrode, and that spark lights the air and fuel mix.

The car battery only gives about 12 volts, which is nowhere near enough to jump that gap under compression. The ignition coil fixes that. It is a transformer with two windings. The engine computer switches current through the primary winding on and off, and every time it cuts the current, the collapsing magnetic field induces a very high voltage in the secondary winding. That voltage goes straight to the plug. On most modern engines there is one coil sitting on top of each plug, called coil-on-plug. Older engines use a coil pack or a single coil with plug leads.

Because the two parts work as a pair, a weak coil can look like a bad plug and a worn plug can kill a coil. A plug with a gap that has grown too wide needs more voltage to fire. The coil works harder to deliver it, heats up and eventually cracks or shorts. That is why many mechanics replace spark plugs and ignition coils together on high-mileage engines, or at least check the coils whenever the plugs come out.

If you want the full engineering background, the spark plug article on Wikipedia covers the history and the physics well.

Iridium vs Platinum vs Copper Spark Plugs

The material on the electrode tip decides how long the plug lasts and how easily it fires.

  • Copper core (nickel tip): cheap and conducts well, but the soft tip wears quickly. Usually replaced every 20,000 to 30,000 miles (about 30,000 to 50,000 km). Mostly found on older engines.
  • Platinum: harder than nickel, so the gap stays stable for longer. A good middle choice and common as original equipment on many Japanese and American engines.
  • Iridium: harder again, with a very fine centre electrode that needs less voltage to spark. Iridium plugs often last 60,000 to 100,000 miles. Most modern engines with coil-on-plug ignition came with iridium from the factory.

The safe rule is to fit the same type your engine came with, or an upgrade. Going from iridium back to copper means you will be changing plugs much more often, and on some engines a copper plug can upset the misfire detection. Most of the spark plugs we sell are iridium or iridium platinum for that reason.

Signs Your Spark Plugs or Ignition Coils Need Replacing

These are the symptoms that usually point to the ignition system. Several of them can also come from fuel or air problems, so read any stored fault codes first.

  • Misfire or check engine light: codes P0300 to P0308 point to misfires. P0301 means cylinder 1, P0302 cylinder 2 and so on. A misfire stuck on one cylinder often means one coil or one plug.
  • Rough idle: the engine shakes at a stop, and the rev needle may wobble.
  • Hesitation when accelerating: the car stumbles or jerks when you press the pedal, especially under load or uphill.
  • Hard starting: the engine cranks longer than normal before catching, or needs more than one try on a cold morning.
  • Higher fuel use: unburned fuel is wasted fuel. A drop in economy with no other cause can be worn plugs.
  • Fuel smell from the exhaust: a dead cylinder pushes raw fuel into the exhaust. Left alone, this can overheat and damage the catalytic converter.
  • Flashing check engine light: this means a heavy misfire. Drive gently and get it fixed soon, because it is the kind that damages the catalytic converter.

How to tell a bad coil from a bad plug

On a coil-on-plug engine there is a simple test. Note which cylinder has the misfire code, then swap that coil with the one next to it. Clear the codes and drive. If the misfire moves to the other cylinder, the coil is the problem. If it stays put, look at the plug, the injector or compression on that cylinder. Glow plugs on a diesel can be checked with a multimeter for resistance, and a failed one usually reads open circuit.

When you pull a spark plug, the tip tells a story. Light tan or grey deposits are normal. Black dry soot means a rich mixture. Wet oil on the tip points to worn rings or valve seals. White blistered tips suggest the engine is running too hot or the plug is the wrong heat range. A cracked white insulator means the plug has to be replaced straight away.

How to Choose the Right Spark Plugs and Ignition Coils

Fitment is the part people get wrong most often, so take a minute on this before you order.

  1. Match the OE or interchange number. The fastest route is the number printed on your old plug or coil. We list OE and cross-reference numbers in our product titles, such as 90919-01253, 22401-5M015, LFR5AIX-11, 12137550012 and 22448-JF00B. If your number matches, the part fits.
  2. Check the engine, not just the model. One car model can come with two or three engines. A Nissan Frontier with the 4-cylinder needs different plugs from one with the V6. Look at the engine code or displacement in your owner's manual or under the bonnet.
  3. Count your cylinders. A 4-cylinder engine needs 4 plugs, a V6 needs 6 and a V8 needs 8. Our sets are sold to match, so you rarely need to buy more than one pack.
  4. Heat range and gap. The heat range is built into the part number. Do not change it unless you have a tuned engine and know why you are doing it. Most iridium plugs come pre-gapped. Check the gap before fitting, but do not lever a fine iridium tip, as it can snap.
  5. Thread and reach. Plugs differ in thread diameter, thread length and seat type. The wrong reach can hit a piston. Using the OE number avoids this problem.

If you are unsure, send us your vehicle year, make, model, engine size and VIN through our contact page and we will confirm the right spark plugs and ignition coils for you before you pay.

Replacing Spark Plugs and Ignition Coils: What the Job Involves

On most 4-cylinder engines this is a job a careful owner can do at home in under an hour. V6 engines with rear plugs under the intake manifold take longer, and some need the plenum removed. Here is the general order of work. Always follow the service manual for your engine.

  1. Let the engine cool fully. Aluminium cylinder heads have soft threads, and removing plugs from a hot head can damage them.
  2. Disconnect the battery if your manual recommends it.
  3. Unplug the coil connector, remove the coil bolt and pull the coil straight up. Do one cylinder at a time so nothing gets mixed up.
  4. Blow out the plug well with compressed air so dirt does not fall into the cylinder.
  5. Remove the old plug with a spark plug socket and extension.
  6. Thread the new plug in by hand first. If it will not turn easily by hand, stop and start again, because it is cross-threading.
  7. Tighten to the torque in the manual. Over-tightening is a common way to strip threads or crack the insulator.
  8. Put a small amount of dielectric grease inside the coil boot, refit the coil and plug in the connector.
  9. Repeat for each cylinder, reconnect the battery, start the engine and clear any stored codes.

Glow plugs on diesel engines need more care. They can seize in the head after years of heat, and a snapped glow plug is an expensive repair. Warm the engine slightly, use penetrating oil and turn gently. If one feels stuck, stop and get a specialist to remove it.

How Often to Replace Spark Plugs and Ignition Coils

Your service schedule is the final word, but these are typical intervals:

  • Copper plugs: around every 20,000 to 30,000 miles.
  • Platinum plugs: around every 60,000 miles.
  • Iridium plugs: around every 60,000 to 100,000 miles.
  • Ignition coils: no fixed interval. Replace when they fail, or as a set on high-mileage engines when one has already gone.
  • Glow plugs: often 100,000 miles or more, but replace any that test bad, and many owners replace the full set at once.

Turbo engines, like the Subaru WRX STi and MINI Cooper S, are harder on plugs and coils. Boost raises cylinder pressure, which makes the spark harder to fire. These engines often need plugs sooner than the brochure says, and coil failure is common on the R56 MINI in particular. If you have added power with a tune, ask your tuner whether a colder plug is needed.

Should You Replace One Ignition Coil or All of Them?

This comes up a lot. If one coil fails on a young engine, replacing just that one is fine. On an older engine, the other coils have seen the same heat and the same hours, so another one often fails within months. Buying a full set, like our 4-piece MINI pack or the 6-piece GT-R set, saves you doing the job twice and keeps all cylinders firing the same way. It also saves you a second round of removing intake parts on engines where the coils are hard to reach.

The same thinking applies to spark plugs. Always replace them as a full set. Mixing a new plug with old ones gives uneven combustion between cylinders.

Related Parts to Check at the Same Time

While the coils are out, it is worth looking at a few nearby parts that affect how the engine runs:

  • Engine air filters: a clogged filter starves the engine and makes a weak spark more noticeable.
  • Oxygen and engine sensors: a lazy O2 sensor can cause a rough idle that feels like a misfire.
  • Fuel injectors: a blocked injector on one cylinder gives the same code as a bad coil.
  • Valve covers and gaskets: an oil leak from the valve cover or plug tube seals can fill the plug wells with oil and short out the coils.
  • Car electrical parts: alternators, starters and other parts that keep the ignition system powered.
  • Engine parts: gaskets, mounts and internal parts if your problem turns out to be mechanical.

Ordering, Delivery and Returns

You can order any of these spark plugs and ignition coils directly from this page. Delivery options and times for your country are shown at checkout and on our shipping page. If a part arrives and does not fit the vehicle listed on the product page, see our returns policy for how to send it back, and our warranty page for cover on faulty parts. Keep the packaging and do not fit a plug or coil until you have compared it with the old one. That makes a return straightforward if anything is wrong.

Spark Plugs and Ignition Coils FAQ

Can I drive with a bad ignition coil?

For a short distance, yes, but it is not a good idea. A dead cylinder sends unburned fuel into the exhaust, which can overheat the catalytic converter. It also puts extra strain on engine mounts because the engine runs out of balance. Fix it as soon as you can.

Do iridium spark plugs give more power?

On a healthy standard engine, not really. What they give is a steady spark for much longer and easier starting as they age. On a worn engine with old plugs, fitting new iridium plugs can bring back power that was lost, which can feel like a gain.

Do I need to gap new spark plugs?

Check the gap with a feeler gauge, but most iridium and platinum plugs come pre-set for the engine they are made for. If you do adjust it, bend only the ground strap and never press on the fine centre electrode.

What is the difference between a spark plug and a glow plug?

A spark plug makes a spark to light petrol. A glow plug is a heating element that warms the combustion chamber of a diesel so it can start from cold. Diesels light the fuel through compression, so they have no spark plugs at all.

Why does my engine misfire only in the rain?

That usually means a cracked coil boot or a coil with a crack in its casing. Moisture finds the crack and the spark leaks to the engine instead of reaching the plug. Replacing the coil normally fixes it.

Can a bad spark plug damage an ignition coil?

Yes. A worn plug with a wide gap needs more voltage, and the coil overheats trying to supply it. Changing plugs on time protects the coils.

How do I know which spark plugs fit my car?

Use the part number on your old plug or the one in your service manual, then match it to the OE and interchange numbers in our product titles. If you are still unsure, contact us with your VIN and we will check for you.

Do you ship spark plugs and ignition coils outside the US?

The countries we deliver to and the cost for each are shown at checkout. Our shipping page has the current details.

Spark Plug Gap and Heat Range Explained

Two numbers decide whether spark plugs suit your engine: the gap and the heat range. The gap is the distance between the centre and ground electrodes. Most modern iridium and platinum spark plugs come pre-gapped, and bending a fine-wire electrode can damage it, so check the gap with a wire gauge rather than forcing it. The heat range describes how quickly a plug sheds heat. A plug that runs too cold fouls with carbon; one that runs too hot can cause pre-ignition. Unless your engine has been tuned or boosted beyond stock, stay with the heat range the maker specifies. That is why we list OE and interchange numbers on every plug, so you can match the exact type your engine was built for.

When you fit new spark plugs, tighten them to the torque in your service manual and use a little dielectric grease inside each ignition coil boot so it seals against moisture. Browse our engine parts for related items such as valve cover gaskets that often leak oil into plug wells.