How often do you do it - Change Spark Plugs

[Rocky]

NB8B is a bit harder starting than it used to be. Cranks for a few seconds longer.
Plugs were last changed 20,000 Ks ago in Aug 2011.
Wondering whether a Plug change might be in order.
(as most of you will be aware, this is a car that does 95% of its mileage on the open road)

[StanTheMan]

when Patchy was the almost stock 1.6 I used to do them every 5000 km.
then when things got tight for a few years I used to clean them at 5000 km and use them for 10000 km. I felt that was seriously pushing it.

I don't think Ive used a spark plug for longer than that. ever. Ive also never used really precious ones either.

when tuning patchy of recent times they got cleaned on the regular basis more due to necessity & my ability & learning how to tune. but Ive not had them in of more than 4000 km....

I mean have you had them out & looked at them?

[Rocky]

No Stan, it was such a production last time that I wasn't keen. My mechanic did it last time and broke little plastic clips on those stupid 'coil-over' things. It doesn't look remotely like what I am used to with previous cars where you just unclip the HT leads and unscrew the plugs.
This looks like you have to undo four 10mm bolts on the plastic things on two of the plugs. Everything is connected together like a monkey puzzle.

[Mr Morlock]

The owners manual defines the service interval. For the NB P2 a must have is the Mazda pdf version of the service manual covering virtually everything. It's free and It's terrific. A proper manual written by engineers with problem solving specs the whole shooting match.
I only recently replaced plugs and it's an easy task.
Check with 93 Clubman for place to find the manual. I do have it but it might be quicker to do it by download off the net. It might even be in the forum tech section- I have not checked.

[Luke]

I will answer the heading.
Only ever had mine changed once at either 60000kms or 70000km's with the timing belt on my SE.
Had no issues at the time, just changed them since so much other stuff was being changed at the time.
Replaced factory NGK Iridium's with NGK Iridium's sourced from 949 when our $ was equal to US $.
A set of 4 in the US was literally the price of one here.
Couldn't see a reason to go with another brand or type of plug when the NGK Iridium's that were in there had no issues.
Cars has 87000km's now.
Oh and lots and lots of track use.

[KevGoat]

In the "ol days" I changed plugs and points (anyone remember those!) with every oil change ... these days with engine improvements and improved manufacturing I find plugs last much longer with no adverse affects. I still take them out and check regular, maybe clean if necessary, and pretty much just replace as needed. I've been more fussy with my MX's, but the SE has the ones that supposedly last 100k and is running fine @ 50k, so haven't even bothered looking at them yet.

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[The American]

Longer cranking sounds like something other than plugs. Battery getting on perhaps?

[JBT]

NB8B is a bit harder starting than it used to be. Cranks for a few seconds longer.
Plugs were last changed 20,000 Ks ago in Aug 2011.
Wondering whether a Plug change might be in order.

If it starts and runs ok without misfire, then I reckon the plugs/coils are fine. The plugs should be good for 40,000+km and the coils should be good for 140,000+km.
I'd be suspecting battery if the cranking is a bit slower or fuel delivery issues if the battery is good.

[Rocky]

Thanks Guys,
Stan & MM - I have the Workshop and Parts Manuals in Hardcopy.
Thanks to my former "mechanic" breaking the plastic connector, it is easy to separate.
I assume it is necessary to undo the 2 X 10mm bolts on each set of what they term "ignition coils" to access the 2nd & 4th plugs.
The Manual doesn't mention this of course because it is not written for 'occasional would-be boy-mechanics' like me.



I will pull them out tomorrow and have a look at them. If I go to this trouble I will replace them anyhow.

With all my other sportscars I used to do it every 10,000 ks but I seemed to remember another thread where there was a big variance in how often people thought the plugs needed to be changed. I thought I remembered it ranging from 10,000 ks to 100,000 ks.
Does anybody put some sort of lube on the thread of new plugs to ensure they can get them out next time?

Yank & JB - The battery is 7 years old. I changed the last one at 7 years - it was still cranking OK but I thought 7 yrs was a decent run.
This one seems to crank OK but just takes a few seconds longer to fire than it did - maybe it's not as strong as it sounds.
It idles fine and revs out nice and smooth and strong, so yeah, maybe battery.

[JBT]

Does anybody put some sort of lube on the thread of new plugs to ensure they can get them out next time?

No Rocky, do not do this.

[Rocky]

Thanks JB - I had a mate who was a bit of a mechanical genius who was fond of putting a bit of Graphite grease on things and I couldn't remember whether he used to put it on plugs. I guess the heat in that area would fry and harden any lube and cause problems.

[Nevyn72]

Only ever had mine changed once at either 60000kms or 70000km's with the timing belt on my SE.

Replaced factory NGK Iridium's with NGK Iridium's sourced from 949 when our $ was equal to US $.

Well actually the SE used an ultra funky Platinum/Iridium plug from Denso (SK 16PR-F8) as OEM, VERY expensive and currently >$70 each from Mazda.....

The service interval is 110K km, yep that's right, you only change them every 110 000 Km!!
I'm now at 114K Km and have a new set ( I scored a box of 4 from the US for A$32 delivered! ) ready to go in with the next oil change @ 115K Km.

[JBT]

Thanks JB - I had a mate who was a bit of a mechanical genius who was fond of putting a bit of Graphite grease on things and I couldn't remember whether he used to put it on plugs. I guess the heat in that area would fry and harden any lube and cause problems.

I was advised to never use anti-seize/lube on plugs because it can lead to over torqueing on installation and the fry/harden issue to which you refer.

[93_Clubman]

NB8B is a bit harder starting than it used to be. Cranks for a few seconds longer.

NB8B longer cranking has come up a few times in the last few years on here, but been a bit elusive to ID: viewtopic.php?f=29&t=75031
Mazda TSB for NB8A longer cranking: https://www.miata.net/garage/tsb/sb003_99.html

battery is 7 years old. This one seems to crank OK but just takes a few seconds longer to fire than it did.

Assume the last couple of batteries haven't been the black OEM Panasonic given replacement around 7 years? Regardless, as mentioned above, battery & fuel filter can be culprits as can the green Main/EGI relay in the engine bay fuse box.

[93_Clubman]

Imagine you'd already be all over this, but also clean with scouring pad & cloth & tighten battery terminals/clamps.
Btw, here's another - NB8B longer cranking has come up a few times in the last few years on here, but been a bit elusive to ID: viewtopic.php?f=29&t=72105&hilit=nb8b+crank%2A