When your ignition coil has a problem, your vehicle will face problems such as misfire, flameout, or difficulty starting. Therefore, the engine performance of the car will be affected by the ignition coil, but many car owners do not understand its working principle and replacement cycle. In this article, we will take you to understand the ignition coil so that you can benefit from it.
What Is an Ignition Coil?
The ignition coil is an indispensable part for starting your vehicle. It is a voltage conversion device. Usually the battery of our car is 12 volts, but the engine needs a high voltage to run normally. At this time, the ignition coil is needed to amplify the low voltage to a high voltage. Most modern cars now have an ignition coil for each cylinder, while older models may share one coil for two cylinders.
Types of Ignition Coils
There are many types of ignition coils, the most common ones are: traditional single coil, ignition coil (COP), coil pack, distributor mounted coil, etc.
- Traditional single coil is mainly used in old cars, most cars before the 2000s use this type. It is a distributor that transmits voltage to all cylinders through a single coil. It is a very simple device.
- Most new models use ignition coil (COP), and each cylinder has a separate coil directly mounted on the top of the spark plug. This design can get spark faster and more reliably.
- Coil pack is a group of coils formed into a unit, each coil powers one or two cylinders. It is generally common in 4-cylinder, 6-cylinder or 8-cylinder cars.
- Distributor mounted coil is similar to the traditional coil, but it is directly mounted on the distributor, which helps to simplify wiring. It can still be found in some old trucks and SUVs.
How a Coil Pack Works?
A coil pack, also known as an ignition coil pack, is a group of ignition coils housed together in one unit. It’s commonly found in modern vehicles with electronic ignition systems. Here’s how it works:
The car’s engine control unit (ECU) sends a signal to the coil pack, telling it when to fire.
The coil pack uses electromagnetic induction to boost the battery’s low voltage to high voltage.
This high voltage is sent through spark plug wires (or directly to coil-on-plug systems) to the spark plugs.
The spark plugs then use this high voltage to create a spark, igniting the fuel-air mixture in the cylinders.
Coil packs are more efficient than older single-coil systems because they allow for precise timing and better engine performance.
How to Test an Ignition Coil?
Testing an ignition coil can help you confirm if it’s faulty before replacing it. Here’s a simple step-by-step method using a multimeter (a tool to measure voltage, resistance, and current):
Tools You’ll Need:
- Digital multimeter
- Owner’s manual (to find coil specifications)
Steps:
- Disconnect the battery: Always start by disconnecting the negative battery terminal to avoid electric shock.
- Locate the ignition coil: Refer to your owner’s manual to find its position (usually near the engine or on the cylinder head).
- Check primary resistance: Set the multimeter to the “ohms” setting. Connect the probes to the coil’s primary terminals (check your manual for which ones). Compare the reading to the manufacturer’s specs (typically 0.5–2 ohms). A higher or lower reading means the coil is bad.
- Check secondary resistance: Connect one probe to the primary terminal and the other to the coil’s high-voltage terminal (where the spark plug wire connects). The reading should match the manufacturer’s specs (usually 8,000–15,000 ohms). A reading of 0 or infinity indicates a faulty coil.
Bad Ignition Coil Symptoms
If your ignition coil is failing, your car will show clear signs. Watch out for these common symptoms:
- Engine misfires: The engine skips or shakes during acceleration, especially at high speeds.
- Difficulty starting: The engine cranks but takes longer to start, or won’t start at all.
- Stalling: The engine shuts off unexpectedly while driving or idling.
- Decreased fuel efficiency: You’ll notice more frequent trips to the gas station as the engine burns fuel inefficiently.
- Check engine light: The ECU detects a problem and triggers the check engine light (codes like P0350–P0362 often indicate coil issues).
- Rough idle: The engine vibrates or runs unevenly when stopped.
Bad Ignition Coil Symptoms
If your ignition coil is failing, your car will show clear signs. Watch out for these common symptoms:
- Engine misfires: The engine skips or shakes during acceleration, especially at high speeds.
- Difficulty starting: The engine cranks but takes longer to start, or won’t start at all.
- Stalling: The engine shuts off unexpectedly while driving or idling.
- Decreased fuel efficiency: You’ll notice more frequent trips to the gas station as the engine burns fuel inefficiently.
- Check engine light: The ECU detects a problem and triggers the check engine light (codes like P0350–P0362 often indicate coil issues).
- Rough idle: The engine vibrates or runs unevenly when stopped.
How to Change a Toyota Ignition Coil (Step-by-Step Example)
Most modern Toyotas use coil-on-plug systems, which are relatively easy to replace. Here’s how to do it for models like Camry, Corolla, or RAV4:
Tools You’ll Need:
- Socket wrench set (usually 10mm socket)
- Screwdriver (flathead or Phillips)
- New ignition coil (matching Toyota’s OEM specs)
- Gloves and safety glasses
Steps:
- Turn off the engine and disconnect the battery: Ensure the car is parked on a flat surface. Open the hood and disconnect the negative battery terminal (use a wrench to loosen the clamp).
- Locate the ignition coils: In Toyotas, coil-on-plug coils are mounted directly on top of the spark plugs, under a plastic cover (if present). Remove the cover using a screwdriver or socket wrench.
- Disconnect the electrical connector: Each coil has a plastic electrical connector. Press the tab on the connector and gently pull it away from the coil to disconnect.
- Remove the coil bolt: Use a 10mm socket wrench to loosen and remove the single bolt holding the coil in place. Set the bolt aside in a safe place.
- Pull out the old coil: Gently twist and pull the coil upward to remove it from the spark plug well. Avoid yanking it to prevent damage to the spark plug or wiring.
- Install the new coil: Apply a small amount of dielectric grease to the base of the new coil (this helps with insulation). Insert the coil into the spark plug well until it sits firmly.
- Secure the coil with the bolt: Tighten the 10mm bolt to hold the new coil in place (don’t over-tighten to avoid stripping the thread).
- Reconnect the electrical connector: Push the connector back onto the coil until you hear a “click” to confirm it’s locked.
- Replace the plastic cover(if removed) and reconnect the negative battery terminal.
- Test the engine: Start the car and let it idle for a few minutes. Check for misfires or warning lights to ensure the new coil works.
