How to Replace Ignition Cables (Spark Plug Wires) in Your Car

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The purpose of your vehicle’s spark plugs is to ignite the fuel and air available in the combustion chamber. They do this because of a signal received from the computer module or distributor cap.

If the ignition cable, or spark plug wire, carrying this signal fails, the operation of the engine becomes mistimed and under-powered. One or more cylinders will may misfire or weaken. Another result of the fuel and air not combusting completely is a buildup of gases and residue in your injectors or cylinders.

The symptoms of failing ignition cables include rough idling, an illuminated Check Engine Light, and a general lack of engine among others. This all can be very easily avoided with a few simple steps.

Part 1 of 1: Replacing the ignition cables

Materials Needed

battery with red and black cables showing

Step 1: Disconnect the battery. Disconnect the negative battery cable to cut power to the ignition cables.

Disconnect the bolt holding the cable to the terminal using a socket or a wrench.

  • Warning: Set negative battery cable aside so that it will not make contact with anything metal, or a connection may be made restoring power to the cables.

location of ignition cables

Step 2: Locate the ignition cables. The cables will be routed from the spark plugs on the top of the cylinders to the distributor cap or module that powers them.

hand removing spark plug

Step 3: Replace the cables. One by one, remove and replace the spark plug wires.

By doing them one at a time, you will not have to worry about accidentally switching the wires.

To remove an old cable, pull directly upward on the boot of the cable on the spark plug end, and then pull upward on the boot connected to the distributor cap or module. Be sure to only pull on the boot; DO NOT pull on the cable itself.

example of a spark plug wire removal tool

  • Tip: If you are sure you are not going to use the old spark plug cables again, you can use a pair of pliers to help you remove them. The pliers will most likely damage the boot and terminal of the old wires, so it is not recommended that you use pliers on any ignition cables you plan to use again. Otherwise, you can do it by hand or with a spark plug removal tool.

examples of different ignition cable lengths

Again, make sure that the length of the cable you disconnected is the same as the length of the new cable. Extra wire is unnecessary and your engine may not have room to compensate.

diagram of firing order of the cables

What is even more imperative than matching cable length is that you do not mix up the order of the ignition cables. The spark signals are sent in a particular order to each cylinder to time when the piston is at top dead center (at the very top of the cylinder). Improper installation of these cables can result in poor combustion or misfiring of the cylinder, which will cause drivability issues and potentially severe damage to the engine.

  • Tip: If the order of the wires ever gets confused, look up the firing order for your exact vehicle for reference.

example of damaged cables

When removing the spark plug or ignition cables, inspect them for signs of other issues with your vehicle. The most easily detected are signs of burning carbon or oil. This would indicate a failing valve cover gasket and/or failing o-rings around the old spark plugs.

To install a new cable, push the new ignition cable boot on one end to the module, and then push the next end onto the spark plug.

spark plug wire grease

  • Tip: If you wish to use spark plug wire grease (dielectric grease), insert a small drop into the new boot before placing it onto the spark plug.

Move on to the next cable and repeat this step.

Step 4: Reconnect the battery. Reattach the negative battery cable to the terminal to restore power.

Hand tighten the retaining bolt and snug it down with a wrench or socket.

Close the hood of the vehicle once you are finished with this step.

Step 5: Test drive the vehicle. With the car in park, start the vehicle. If the idle is holding steady between 600 and 1,000 RPMs, go for a test drive and observe your vehicle’s drivability.

  • Note: Listen for stuttering, rough idling, and misfires, and feel for any sluggishness.

The ignition system on your vehicle plays a very large role in its operation. Issues with the ignition system are going to slow down and depower your engine. Extended use under these conditions will cause various damages and wear out other parts involved. If you follow the steps laid out in this guide, you can fix these issues and avoid further damage. However, if you’d prefer to have a professional perform this repair, you can always count one of the certified technicians at YourMechanic to properly replace your ignition cables for you at home or at the office.

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11 years of experience
151 reviews
11 years of experience
Mercedes-Benz ML430 - Ignition Cable (Spark plug wires) Replacement - Kennesaw, Georgia
COLLINS was very knowledgeable and worked hard on fixing my car which is now running GREAT!!! I have more work I need to book with YourMechanic and I would like to request COLLINS for all duture work!!!!!
Toyota Camry - Ignition Cable (Spark plug wires) - Smyrna, Georgia
He was timely (often early), friendly, and went about his business. I would have him over again if needed.


32 years of experience
69 reviews
32 years of experience
Chrysler PT Cruiser - Ignition Cable (Spark plug wires) - Hemet, California
Super professional and very skilled. Showed up on time and was very friendly, and even tho he was not sent out with the right parts, and needed to leave to get them (not his fault), the job was still done on time and I am super pleased
Honda Civic - Ignition Cable (Spark plug wires) - Murrieta, California
Absolutely phenomenal mechanic! Was able to complete repairs in half the time that had been estimated and was very knowledgeable! Thank you William!


29 years of experience
223 reviews
29 years of experience
Oldsmobile 98 - Ignition Cable (Spark plug wires) - Tempe, Arizona
Terry was the best mechanic I've had. Instead of just fixing the problem and leaving he spent the extra time yo fix additional problems so the car would be in top shape.
Chevrolet Avalanche 1500 - Ignition Cable (Spark plug wires) - Mesa, Arizona
Friendly and professional. Terry is a skilled and knowledgeable tech. Explains as much (or as little) as the owner wants to know and puts it in understandable terms. He's also organized and methodical about his processes when working on a vehicle, which is the sign of a good technician. I will be having Terry back.


11 years of experience
347 reviews
11 years of experience
Ford Aerostar - Ignition Cable (Spark plug wires) - Indianapolis, Indiana
Bryant was professional and knowledgeable , fixed my auto issue no problem would recommend Bryant to other people

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