1999 Toyota Tacoma: Ignition Coil Replacement Guide

Nov 17, 2025 by Alex Braham 52 views

Hey guys! Are you experiencing some engine troubles with your trusty 1999 Toyota Tacoma? Is your engine misfiring, running rough, or just not performing like it used to? One potential culprit could be a faulty ignition coil. Don't worry; replacing it is a job you can totally handle yourself with a bit of know-how and the right tools. This guide will walk you through the process of replacing the ignition coil on your 1999 Toyota Tacoma, so you can get back on the road with confidence.

Understanding Ignition Coils

Before we dive into the replacement process, let's quickly cover what ignition coils do and why they're important. Ignition coils are a vital part of your engine's ignition system. Their primary function is to transform the low voltage from your battery into the high voltage needed to create a spark at the spark plugs. This spark ignites the air-fuel mixture in the engine's cylinders, which is what makes your engine run. Without a properly functioning ignition coil, your engine won't be able to generate the necessary spark, leading to misfires, poor performance, and potentially even a no-start condition.

Symptoms of a Failing Ignition Coil

Recognizing the symptoms of a failing ignition coil is crucial for diagnosing the problem accurately. Here are some common signs to watch out for:

Engine Misfires: This is perhaps the most noticeable symptom. A misfire occurs when one or more cylinders in your engine fail to fire correctly. This can cause a jerking or sputtering sensation, especially during acceleration.
Rough Idling: If your engine idles roughly, vibrates excessively, or stalls frequently, it could be a sign of a failing ignition coil. The engine may struggle to maintain a consistent idle speed.
Poor Fuel Economy: A faulty ignition coil can cause incomplete combustion, leading to a decrease in fuel efficiency. You may notice that you're having to fill up your gas tank more often than usual.
Check Engine Light: The check engine light is your car's way of telling you something is wrong. If an ignition coil is failing, the check engine light will often illuminate. You can use an OBD-II scanner to read the diagnostic trouble codes (DTCs) and confirm if an ignition coil is the issue.
Loss of Power: A failing ignition coil can result in a noticeable decrease in engine power, especially when accelerating or climbing hills. The engine may feel sluggish and unresponsive.

Tools and Materials You'll Need

Before you start, gather all the necessary tools and materials. Having everything on hand will make the process smoother and more efficient. Here's what you'll need:

New Ignition Coil: Make sure to purchase a replacement ignition coil that is specifically designed for your 1999 Toyota Tacoma. Check your vehicle's make, model, and engine type to ensure compatibility.
Socket Set: You'll need a socket set with various sizes to remove the bolts and nuts that secure the ignition coil. A 10mm socket is commonly used.
Wrench Set: A set of wrenches will be helpful for loosening and tightening bolts in tight spaces.
Screwdrivers: Both flathead and Phillips head screwdrivers may be needed to remove any covers or fasteners.
Multimeter (Optional): A multimeter can be used to test the old ignition coil and confirm that it is indeed faulty.
OBD-II Scanner (Optional): An OBD-II scanner can be used to read diagnostic trouble codes (DTCs) and clear them after the replacement.
Gloves: Wearing gloves will protect your hands from dirt, grease, and potential cuts.
Safety Glasses: Safety glasses will protect your eyes from debris and potential hazards.

Step-by-Step Ignition Coil Replacement Guide

Now that you have your tools and materials ready, let's get started with the replacement process. Follow these step-by-step instructions to replace the ignition coil on your 1999 Toyota Tacoma:

Step 1: Disconnect the Negative Battery Terminal

Safety first! Before working on any electrical components, it's essential to disconnect the negative battery terminal. This will prevent any accidental electrical shocks or damage to your vehicle's electrical system.
Locate the negative battery terminal (it's usually marked with a "-" sign).
Use a wrench to loosen the nut on the terminal clamp.
Carefully disconnect the terminal clamp and tuck it away from the battery post to prevent accidental contact.

Step 2: Locate the Ignition Coil

The location of the ignition coil can vary depending on your engine type. On the 1999 Toyota Tacoma, the ignition coil is typically located on top of the engine, near the spark plugs.
Refer to your vehicle's repair manual or online resources for the exact location of the ignition coil.
Once you've located the ignition coil, take a good look at it and its surroundings. Note the position of any wires, connectors, and mounting hardware.

Step 3: Disconnect the Electrical Connector

Before removing the ignition coil, you'll need to disconnect the electrical connector that is attached to it.
Locate the electrical connector on the ignition coil.
Press the release tab on the connector and gently pull it away from the ignition coil. Be careful not to damage the connector or the wiring.

Step 4: Remove the Mounting Hardware

The ignition coil is typically held in place by one or more bolts or screws.
Use a socket or wrench to remove the mounting hardware.
Keep the hardware in a safe place, as you'll need it to install the new ignition coil.

Step 5: Remove the Old Ignition Coil

With the mounting hardware removed, you should be able to carefully lift the old ignition coil out of its position.
If the ignition coil is stuck, try gently wiggling it back and forth to loosen it.
Be careful not to damage any surrounding components when removing the ignition coil.

Step 6: Install the New Ignition Coil

Now it's time to install the new ignition coil. Make sure you're using a replacement coil that is specifically designed for your 1999 Toyota Tacoma.
Carefully position the new ignition coil in the same location as the old one.
Align the mounting holes and re-install the mounting hardware. Tighten the bolts or screws securely, but don't overtighten them.

Step 7: Reconnect the Electrical Connector

Reconnect the electrical connector to the new ignition coil.
Make sure the connector clicks into place, indicating that it is securely attached.

Step 8: Reconnect the Negative Battery Terminal

Reconnect the negative battery terminal to the battery post.
Tighten the nut on the terminal clamp securely.

Step 9: Start the Engine and Test

Now it's time to start the engine and test your work.
Turn the ignition key and start the engine.
Listen for any unusual noises or vibrations.
If the engine starts smoothly and runs without misfires, congratulations! You've successfully replaced the ignition coil.
If the engine still misfires or runs rough, double-check your work and make sure all connections are secure. You may also want to use an OBD-II scanner to check for any diagnostic trouble codes (DTCs).

Additional Tips and Considerations

Here are a few additional tips and considerations to keep in mind when replacing the ignition coil on your 1999 Toyota Tacoma:

Replace Spark Plugs: When replacing an ignition coil, it's often a good idea to replace the spark plugs as well. Faulty spark plugs can put extra stress on the ignition coils, causing them to fail prematurely.
Use Dielectric Grease: Apply a small amount of dielectric grease to the electrical connector before reconnecting it. This will help protect the connection from corrosion and ensure a good electrical contact.
Consult a Professional: If you're not comfortable performing this repair yourself, or if you encounter any difficulties, don't hesitate to consult a qualified mechanic. They have the expertise and tools to diagnose and repair any issues with your vehicle's ignition system.

Conclusion

Replacing the ignition coil on your 1999 Toyota Tacoma is a straightforward repair that you can often do yourself. By following these step-by-step instructions and taking your time, you can save money on labor costs and get your Tacoma back on the road in no time. Remember to always prioritize safety and consult a professional if you're unsure about any part of the process. Good luck, and happy wrenching!