In 2006, the Mazda Miata MX-5 underwent a significant overhaul, both on the surface and under its skin. With this overhaul came the elimination of the 1.8-liter engine that gave the previous generation a respectable 142 horsepower and 125 foot-pounds of torque. In came a 2.0-liter engine that added more pep to the Miata’s step, thanks to its extra 28 horsepower and 15 foot-pounds of torque. This 2.0-liter engine uses a coil-on-plug ignition system and you need to replace its spark plugs every 120,000 miles to help keep this engine running at its peak efficiency.
Items you will need
- 4 new Mazda L3G2 18 110, or equivalent spark plugs
- Spark plug gap tool
- Socket set
- Spark plug socket
- 6-inch extension
- Torque wrench
- Dielectric grease
- Small flat-head screwdriver
- Inch-pound torque wrench
Check the gap on all four new Mazda L3G2 18 110, or equivalent spark plugs, using a spark plug gap tool. Mazda allows for a gap range from 0.050 to 0.053 inches. If any spark plugs do not meet this specification, exchange them for new plugs, as you cannot adjust the gap on them.
Pull upward on the left and right sides of the engine cover to unlatch it from its mounting points, and remove it from the engine compartment. Allow the vehicle to sit until the engine is cool to the touch.
Trace the upper suspension bar – the thick metal bar spanning between the two strut towers – until you find its center section. Remove the two nuts securing the center section to the Miata’s body, using a ratchet and socket, and remove the center section. Remove the three nuts securing each outer section of the upper suspension bar to the Miata’s body and remove both sides of the suspension bar.
Unplug the four electrical connectors plugged into the four ignition coils – the electrical components in a straight line on the center of the valve cover. Remove the bolt securing each coil pack to the engine, using a ratchet and socket, and pull each coil pack upward with a slight twisting motion to remove it from the spark plug.
Remove the front-most spark plug, using a ratchet, spark plug socket and a 6-inch extension. Pull the plug from the tube, using the spark plug socket. Press a new spark plug into the spark plug socket until its rubber insert secures the plug, then thread the spark plug by hand until it is snug. If you feel any resistance or binding while threading the plug, remove it and thread it again. Attach a torque wrench to the extension and spark plug socket, and tighten the spark plug to between 8 and 10 foot-pounds. Repeat this step on the remaining three plugs in the engine.
Apply a dab of dielectric grease to the inside of the rubber boot on the base of each ignition coil and spread the grease around with a small flat-head screwdriver. Alight each ignition coil with the top of each spark plug – there is no specific order that you have to install the coil packs in – and press each coil pack downward until you feel it click into place.
Hand-thread each coil pack bolt, then tighten it to between 54 and 83 inch-pounds, using an inch-pound torque wrench. Plug the wiring harnesses back into the coil packs. Each harness is only long enough to plug into one coil pack, to prevent you from accidentally plugging them in incorrectly.
Reinstall the two outer portions of the upper suspension bar with the “RH” and “LH” stampings facing upward on the passenger and driver side, respectively. Thread the three retaining nuts, then tighten them to between 12 and 20 foot-pounds, using a torque wrench. Install the center section of the upper suspension bar onto its retaining studs and hand-thread its retaining nuts. Tighten these nuts to between 12 and 20 foot-pounds.
Align the clip on the lower passenger side of the engine cover up with its retaining dowel on the passenger side of the engine compartment and the rubber grommets on the driver side of the cover with their retaining pins on the driver side of the engine. Press the engine cover downward until it snaps into place. Pull upward lightly to verify that you seated the cover fully.
- Never attempt to remove the spark plugs while the engine is hot, as this can cause damage to the cylinder head.
- ProDemand: 2006 Mazda Miata MX-5 Spark Plug Removal and Installation
- Mazda USA: 2006 Mazda Miata Owner’s Manual (see pg 10-4)
- Mazda USA: 2006 Mazda Miata Owner’s Manual (see pg 2)
- Concept Carz: 2006 Mazda Miata MX-5
- Motor Trend: 2006 Mazda Miata MX-5 Specs
- Motor Trend: 2005 Mazda Miata MX-5 Specs
- China Photos/Getty Images News/Getty Images