Spark Plug Replacement, BJ

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Updated February 2011

Tools and Materials Required
3/8" drive torque wrench
3/8" drive ratchet
3" long extension attached to a 10 mm socket to remove and install the coil pack mounting bolts
6" extension attached to a 5/8" (16 mm) spark plug socket to remove and install the spark plugs
spark plug anti-seize lubricant and dielectric tuneup grease (I used Permatex brand)

Ignition System Configuration
There are two coil packs and each has a low-tension connector at one end and a high-tension spark plug lead at the other end. See photos below for a detailed view of the layout. One coil pack (incidently, Mazda refers to them simply as ignition coils) is mounted over, and energizes, the spark plug for No. 2 cylinder and is held in place on the cam cover with two mounting bolts. Its high-tension lead (the short one) connects to and energizes the no. 3 cylinder spark plug. The second coil pack is similarly mounted over the no. 4 cylinder spark plug and its high-tension lead (the long one) connects to the no. 1 cylinder spark plug. Underneath each coil pack, is a spring which applies pressure to a plug cap that physically and electrically connects the coil pack to the spark plug. Each high-tension wire has a similar plug cap, complete with boot (without the spring), integral with the wire. Because of this configuration, the system requires only two spark plug leads.

Spark Plugs
According to the FSM, the OEM specified plug for the FS-DE normally aspirated engine is the NGK V-Power BKR5E-11 or the Denso K16PR-U11 with nickel alloy (commonly, but erroneously, referred to as copper) electrodes. Alternatively, if you're following TheMAN's recommendation for substitution of an extended projected tip type (as I did), substitute the NGK V-Power NGK ZFR5F-11 (which is OEM for the 1.6 L ZM-DE engine) in place of the FS-DE factory recommendation.
http://www.imazda.com/forums/showthread.php?t=142

The electrode gap for either type is OEM specified as 1.0-1.1 mm (.040"-.043"). I purchased my plugs from Mazda (part no. 0000-18-F287) and checking the gap with my wire gauge found all 4-plugs to be right on spec. Again, this is the part no. for the extended projected tip plug; the OEM recommended plug has a different Mazda part no. An excellent online source for our spark plugs is:

http://sparkplugs.com

Precious metal (platinum and iridium) electrode plugs are also available for either of the above applications.

The OEM specified plug for the FS-DET (MSP) turbo engine is the NGK Laser Platinum PZFR6F-11 with a platinum center electrode and a platinum disc welded onto the ground electrode. This is an extended projected tip plug rather than the projected tip type used in the FS-DE, and one heat range colder (a 6 rather than a 5 in the plugs nomenclature). Don't substitute with a nickel alloy type here. The electrode gap is the same as above, 1.0-1.1 mm (.040"-.043").
http://ngksparkplugs.com

Proceedure
For safety, first disconnect the negative battery cable. Begin by disconnecting the low-tension wire plugs from the sockets at the ends of the coil packs and then disconnect the high-tension wires from their associated spark plugs by pulling the plug boots (not the wires) straight up. Next, to gain access to the no.2 and no. 4 cylinder spark plugs, remove the coil packs from the cam cover by removing their mounting bolts with the ratchet, 3" extension and 10 mm socket. To avoid damage because of the short length of the high-tension lead that connects the no. 3 cylinder spark plug to the coil pack, before disconnecting this lead unbolt the coil pack and pull it up while simultaneously pulling up on spark plug no. 3 lead's boot. In this way you'll prevent sharply bending the spark plug wire and possibly degrading or breaking the conductor.

After disconnecting the coil packs from their respective spark plugs and moving them out of the way, all 4-spark plugs can be removed using the ratchet, 6" extension, and the 5/8" spark plug socket. The 6" extension is required because the spark plugs are deeply recessed. All spark plug manufacturers recommend that removal of the old plugs from aluminum cylinder heads only be done when the engine is cool. Since aluminum and steel have different expansion and contraction rates, removing spark plugs from a hot cylinder head can cause damage to the threads. Upon removal, it turned out that the old plugs were Denso K16PR-U11 that, according to the FSM, are equivalent to NGK BKR5E-11 both of which are OEM specified, as stated above. After removing the old plugs, if any appreciable time goes by before installing the new ones, it's a good idea to cover the plug holes with a rag to prevent the falling in of debris.

Alternatively, to reduce the number of components that have to be dealt with at one time, the no. 2 coil pack along with the no. 1 and 3 spark plug leads can be removed, and the spark plugs for cylinder nos. 1 through 3 can be removed and replaced while leaving the no. 4 coil pack in place. Then, the no. 4 coil pack and its spark plug can be worked on separately.

Before installing the new plugs, coat the threads with Spark Plug Anti-Seize Lubricant. This will prevent binding, possible thread damage, and worst case, even stripping during subsequent plug removals. Remember, the heads are aluminum. Of course, make sure the anti-seize is placed only on the threads and not on the spark plug electrodes.

Important Note
It has recently come to my attention that spark plug manufacturers do not recommend the application of anti-seize to spark plug threads before installation. For example, NGK states that all their plugs are manufactured with a special metal shell (trivalent) plating to prevent damage to aluminum cylinder heads. Since anti-seize acts as a lubricant, applying it to the threads will cause the installer to inadvertantly over-torque the plug stretching the metal between the last thread and the seal between the cylinder head and plug. This increases the probability that the spark plug will either break during installation or upon removal. All spark plugs recommended for our engines including those from Denso and other manufacturers have this special plating and therefore should also not have anti-seize applied. For more information, go to:
http://www.wihandyman.com/forum/showthread.php?t=51691

I know many of us, myself included, have routinely been applying anti-seize at every plug change and old habits die hard. I would advise that those who want to continue this practice apply the lightest coating possible and torque the plugs to the lower end of the torque range specification to guard against overtightening. What should you do? You'll have to decide for yourselves. My belief is that provided a torque wrench is used, based on this new information and my own prior experience, either installing plugs dry or using a judicious amount of anti-seize will both yield satisfactory results. How's that for weaseling?

Proceedure Continues
When installing the plugs, insert the new plug into the spark plug socket and thread the plug into the head by turning the extension by hand until the plug is hand tight. This will help guard against cross-threading and damaging the threads as could occur if a wrench were used for the initial tightening. Once the plug is hand tight, attach the torque wrench to the extension and tighten to the FSM specification of 11-16 ft/lbs (15-22 N-m). I split the difference and tightened the plugs to 13.5 ft/lbs.

Prior to reinstalling the coil packs, coat the four mounting bolt threads with anti-seize to insure easy removal during the next spark plug change. Be careful when tightening the coil pack bolts as the FSM recommended torque setting is only 69.5-95.4 in/lbs (7.9-10.7 N-m) which works out to 6-8 ft/lbs. Since this is close to the lower limit of my torque wrench, I opted to just snug up the bolts with my ratchet. Reattach the low-tension wires to the coil packs but before connecting the high-tension leads to the spark plugs for cylinders no.1 and 3, coat the inside of the boots with Dielectric Tune-up Grease which prevents sticking and possible boot damage on subsequent removals.

Finish by reattaching the negative battery cable.

The first photo below is a view of the relevant ignition system compnents showing the two coil packs and the two spark plug wires.

The second photo is a closeup of one of the coil packs showing the low- tension connector on the left side, the high-tension lead connection on the right side, and the two mounting bolts.

The third photo shows both low-tension wire plugs disconnected from their respective coil packs. Cylinder #2 coil pack has been unbolted from the valve cover, disconnected from its spark plug, and moved out of the way. Cylinders #1 and #3 spark plug wire plug caps have also been disconnected from their respective spark plugs. These operations allow access to the spark plugs for cylinders #1, 2 and 3 for removal and replacement. The coil pack for cylinder #4 is still in place.

The final photo shows the cylinder #4 coil pack unbolted from the valve cover, disconnected from its spark plug, and moved out of the way allowing access to the spark plug for removal and replacement.

Happy Motoring!

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Replacement Interval

How often should spark plugs be replaced?

The FSM lists two Scheduled Maintenance Tables:
Schedule 1 - (Normal driving conditions) U.S.A.
Schedule 2 - Canada, Puerto Rico and (Unique driving conditions) U.S.A.

In both cases, it's recommended that spark plugs be changed every 30,000 miles (48,000 km). However, this recommendation applies only to the V-Power nickel alloy electrode types (the only ones listed in the FSM). Platinum and iridium electrode types have a much longer service life since those materials take much longer to burn off.

Happy Motoring!

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Upgrading the Spark Plugs

Subsequent to posting this thread, I decided to replace my OEM nickel alloy spark plugs with a precious metal electrode type. My purpose was to determine if in fact a performance benefit could be obtained as asserted both from a technical standpoint and as claimed by the manufacturers, as well as being able to provide some data of interest to our Forum members. The extra longevity is of secondary importance to me as I don't mind changing spark plugs but of course that may be a primary concern to others.

The major benefit claimed by both NGK and Denso with respect to iridium/platinum electrodes, aside from longevity, is a reduction in "quench" resulting in a smoother more rapid burn of the A/F mixture leading to more complete combustion. This in turn would provide better performance as well as lower emissions. For a more detailed discussion of this phenomenon, go to:

http://www.wihandyman.com/forum/showthread.php?t=46140

NGK and Denso spark plugs with precious metal electrodes are available in the following configurations:
1. Single platinum with platinum-tipped center electrode and nickel alloy ground
2. Double platinum with platinum-tipped center electrode and nickel alloy ground with platinum pad
3. Iridium-tipped center electrode and nickel alloy ground
4. Long life Iridium-tipped center electrode and nickel alloy ground with platinum pad

For the greatest potential performance increase I chose to go with type #4. Consequently, I ordered 4 Denso SKJ16CR-L11 Long Life iridium/platinum plugs at a cost of US $11.95 each for a total of $47.80 + $9.42 shipping for a grand total of $57.22. I bought them at:

http://www.sparkplugs.com

These plugs are the iridium/platinum version of the extended projected tip type used in the 1.6 L ZM-DE engine that, as I explained above, I'm using in place of the OEM specified plug for the FS-DE engine. There is no NGK spark plug suitable for this application. While NGK IZFR5F-11 (extended projected tip, correct reach, heat range and gap) exists, it is not available in the US. According to TheMAN it's sold only in Japan. That's not a problem - NGK and Denso both make superior products.

For those seeking an upgrade to the OEM specified plugs in either the 1.8 L FP-DE or 2.0 L FS-DE engines, either of these two iridium/platinum plugs would be suitable:
NGK IFR5E-11
Denso SK16PR-L11

Although the 2.0 L FS-DET engine uses OEM double platinum plugs, those wishing to switch to a long life iridium/platinum type can use:
NGK IZFR6F-11

For a more complete list of suitable spark plugs for BJ, go to:

http://www.wihandyman.com/forum/showthread.php?t=46112

The nickel alloy NGK ZFR5F-11 plugs I removed were like new aside from the coloration due to the combustion process. The electrodes, which were a light chocolate brown in color, showed no sign of wear and the gap was virtually on spec. Obviously the heat range is correct for my engine's operating conditions. None of this is surprising as the old plugs only had 17,359 miles on them. I've posted photos below so you can judge for yourselves. I've also posted photos of the iridium plugs to demonstate how they differ from conventional nickel alloy types.

In the photos below of these extended projected tip plugs, the much smaller diameter of the iridium center electrode can be seen and compared with that of the nickel alloy type. The platinum pad ground electrode can just barely be made out in photo #2. Note also the "correct" plug color of the used plugs removed from the engine.

Happy Motoring!

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Driving Impressions

After installation I set up a road test mission of about 40 miles - 15 on the Interstate and 25 on 2-lane highways. This gave me a good chance to test during a variety of driving modes. Almost immediately, I did notice two distinct changes: noticeably faster throttle reponse and somewhat increased acceleration off the line, through the gears, and within a single gear (for example, 60 to 80 mph in fifth gear).

Although one could attribute this seeming performance increase to the sole consequence of having new plugs, the still excellent condition of the old ones leads me to believe that the increase is due to the structural changes in the iridium plugs rather than to the fact that they are new.

Both Denso and NGK claim for their iridium/platinum plugs better acceleration, easier starting, better fuel mileage, and even increased power output (or at least allowing the engine to develop its full power capability), for technical reasons discussed elsewhere on this Forum. It would seem that, at least in terms of acceleration, they may have a point. At that point, it was too soon to tell about their other claims (and my engine had always been easy starting anyway) but only time will tell.

Extended testing and putting some miles on the car after changing to the Long Life iridium plugs demonstrated that my first impressions were correct - a definite increase in acceleration in all modes and faster throttle response.

I also thought that the idle was a bit smoother with perhaps a tad less vibration in the stick. Remembering that I have a digital tach in my car, with a fully warmed-up engine regardless of ambient or air box temperature, and with headlights either on or off, the idle speed always transitions between 690 and 700 rpm and never deviates outside this range. With the new plugs, although I sense a smoother idle, the tach readings are the same as before, indicating apparently no decrease in variability. A minor point but I thought it was interesting to mention.

I can't say that the engine starts more readily as I still haven't detected any difference, but as previously stated my engine always was an easy starter except when the ambient drops to the low teens or single-digits F.

The only remaining question is whether the new plugs will aid in reducing fuel consumption but I haven't tested this parameter, to date.

I feel the gain in performance was significant enough to justify the extra cost of these plugs, quite apart from their longer life expectancy.

Happy Motoring!