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Spark Plug replacement on a 300zx 89-96

Updated on May 5, 2016

Spark Plug Replacement:

Change the sparkplugs on your 300Zx. Changing out your spark plugs are easy. When adding more HP performance modifications, upgrading to a 'cooler' spark plug will make the car run smoother and avoid damage due to high rpms. Please note to replace your sparkplugs with NGK brand plugs or you will risk having all sorts of problems with hesitation or other engine problems.

Intervals for changing your Spark Plugs:

The factory service manual (FSM) recommends removing and replacing your sparkplugs every 60k miles.

Part Numbers: N/A= Naturally Aspired(Non Turbo) TT= Twin Turbo

Hot type 6x (NA) PFR5B-11/ 6x (Twin Turbo) PFR5B-11B

Standard type 6x (NA) PFR6B-11/ 6x (Twin Turbo) PFR5B-11B

Colder types 6x (NA) PFR7B-11 / PFR6B-11/ 6x (Twin Turbo) PFR6B-11C

Recommended Tools:

Sparkplug socket (16mm) and Wrench


1. Unscrew and remove the bracket holding the cruise control cable to the intake balance tube.

2. Remove the small vacuum line that connects the passenger side fuel pressure regulator to the intake balance tube.

3. Locate the zip tie holding the wiring harness to the driver's side of the intake balance tube and remove it.

4. Using the appropriate socket remove the bolts/nuts connecting the balancetube to the plenum (three x 12mm nuts, two 12 mm bolts ) move the wire harness straps and tubing braces off the top of the balance tube flanges and 'flop' the balance tube toward the windshield. Be careful not to lose the three sealing O-rings they provide a seal to the plenum against the balance tube. Cover the balance tube openings with tape, you don't want anything going into plenum and the intake.

5. Disconnect all of the coil pack plug wires.

6 Each coil pack has two holding bolts (12 x 12mm). You need to Remove all bolt before you can remove the ignition coil packs. Be careful pulling off the Coil packs they can be damaged if handled rough.

7. Use a gapping tool to check the gap the on the spark plugs, mistakes are sometime made and the sparkplug gap could be off .The Stock gap is .044" be gentle with the tiny electrode it can be damage. You will be increasing or decreasing the gap by moving the top metal piece not the center electrode.

8. Righty tighty(clockwise), Lefty losey (counter clockwise). Loosen the spark plug by turning your 16mm socket left/CCW to remove each plug. Remove the old Sparkplugs and insert the new ones. If the old ones don't come out easily due to the lack of gripe of the socket use a rubber fuel hose to stick on the end of the plug to lift them out gentle. The new sparkplug should be started gently, use ant seize on the plugs and don't cross thread them. Recommended Torque is 14-22 ft-lbs.

9. Reinsert all the coil packs and their bolts.

10. Plug in coil pack wires.

11. The balance tube should be installed with the three O-ring gaskets. Be careful not over torque the steel bolts into the aluminum plenum. Reinstall the wiring harness brackets over the studs (5 x 12mm). Torque to 12-15 ft-lbs.

Above are 2 Sparkplugs for your 300zx, Notice that the NGK Sparkplug on the bottom is longer. These plugs were designed to be long enough to fire in the cylinder correctly the shorter plug may not ignite the fuel properly.

Please see the picture below. By looking at the sparkplugs you can determine if your engine is having any type of problems. A fouled oily sparkplug electrode could mean you burning oil due to a bad seal.

Also, remember to put the Coilpacks on the correct plugs. Its pretty easy to figure out due the lengths of the wires but below are some pictures that can help you if you get in a bind.

I hope these instructions help. If anyone has any questions send me an email at


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