How do I change the spark plugs on a Mazda RX-7 FD?

Difficulty: Easy to Moderate

Safety Warning: If you choose to work from underneath the vehicle, ensure the car is safely secured on four good-quality jack stands or use front wheel ramps ¹. Do not jack up just one corner, as this can put damaging loads on the flimsy OEM swaybar mounts ².

Changing the spark plugs on an FD RX-7 is a straightforward job. The plugs are located on the left (driver's) side of the engine block, below the throttle body ¹.

Here is how to get the job done right:

1. Choosing the Right Spark Plugs

For a stock or near-stock FD, use standard NGK spark plugs:

• Leading (Bottom Two Plugs - L1 & L2): NGK BUR7EQP (Heat Range 7) ²
• Trailing (Top Two Plugs - T1 & T2): NGK BUR9EQP (Heat Range 9, marked with blue stripes) ¹

Note: It is absolutely critical not to mix these up. Running a hotter heat range 7 plug in the trailing position can cause detonation and potentially blow the engine ². If your car has bolt-on modifications and runs higher boost, you should switch to heat range 9 plugs in all four positions ².

2. Access Methods

You can access the plugs from either the top or the bottom of the engine bay:

• From the Top: This method takes about 20 minutes ². For easier reach, it is recommended to take off the intake/throttle body elbow ¹. The elbow seals with an O-ring, which is reusable, so you will not need to buy a new gasket ².
• From the Bottom: Moving underneath the car provides a clear view through a large access hole under the driver's side of the engine ¹. This angle makes it easier to cleanly remove and properly torque the plugs ².

3. Removal and Installation

• Tools: You only need a standard socket wrench and a standard spark plug socket. A thin-walled socket is not required for normal NGK plugs ².
• Wires: Pull and change the spark plug wires one at a time so you don't get the firing order mixed up ¹. Make absolutely sure the trailing cords are not installed backward ¹.
• Anti-Seize: Apply a small dab of anti-seize compound to the threads of the new plugs. This is a must to prevent them from seizing in the engine block later ².
• Torque: The torque spec for the plugs is very low, around 10-15 ft-lbs. To avoid over-tightening, grip the middle of your socket wrench handle and just snug the plug up tight ².