mazdaexe

will cleaning these spark plugs do any good? or should I just get a replacement?
thanx

expo1

How many miles were on them?
https://www.rx8club.com/attachment.p...chmentid=62520 is a photo of my last set with 32,000 miles on them. The car was running ok so I guess "dirty plugs" is normal? I just changed them because I hit 50,000 miles. I plan to change them again at 100,000.

willhave8

Holy crap!!! You have 50K miles on your car???

At best that is 20K per year at worst over 25K per year. Even in the commuting crazy NE, that is crazy...

Lucky you

Go48

Assuming there are no mechanical problems with the plugs, like a cracked ceramic insulator, theoretically you can clean them--particularly the carbon buildup on the center insulator--gap them and they should be OK. Can't see the center ceramic insulator, but if it is covered in black, shiney carbon material it will be difficult to remove that completely, and that's critical. Personally, I would toss them into the trash can and spend the $$$ to get new ones.

Nubo

Anyone know what's that white crusty stuff? I notice it on other sparkplug pics from the 8. Is that ash deposits from burning oil?

btw, bong, what oil do you use?

xrider01

how much do the NGKs go for?

mazdaexe

Nubo, I used Castrol 5W20 non-syn before. For the last 2 oil changes, I used pennzoil.

Around after 22000 miles, my car is getting more backfire/popping, worsen gas mileage (about 2mpg less) and seems to have loss some power (butt dyno).

I just cleaned the plugs and put them back in. I havent really tried it out yet, but it seems throttle response is better and high end power is back (still need to find a safe place to test that out again). Will check the MPG when I finish this tank of gas.

Thanks for the responses, more feedback welcomed.

Glyphon

$120 per set of 4 from the dealer (not including installation).
$87 shipped for set of 4 from sparkplugs.com.

mazdaexe

According to sparkplugs.com, there are some denso plugs available. would these be any better than stock? thanx

army_rx8

i thought the car's manuel says to replace the plugs at 35k miles (fo rheavy driving)...that's when i replaced mine. but my plugs didn't look tha tbad when i changed them out. i woudl replace them...but tha tis just me.

Glyphon

No. those are for racing/heavily modded cars. from what i understand, everyday drivability for stock/lightly modded cars would suffer. i think i recall reading that the reason for this is they are a different temperature range than stock.

and as for changing the plugs, there's been a bit of variety on that. some people changed theirs around 10-15k miles and found heavy build up. dealer changed mine at 26.8k miles when i went in for a misfire cel.

mazdaexe

From sparkplugs.com, they offer two different set of plugs. one set the same as stock heat range, the other set, 1 heat range colder.

Glyphon

one of those denso sets is new, but i'm not sure which one. when i ordered plugs from them a month ago, there was only 1 set of denso on the site.

you can try it if you want.
if you do, report back with how they work for you

mazdaexe

haha. Im not sure if I wanna be the first test monkey, but Im still quite far away from mazdas scheduled spark plug replacement.. perhaps I will give it a shot. let you guys know. :]

TeamRX8

iTrader: (25)

I only have 3,000 miles and have changed them twice already

Glyphon

stop flooding your car (just a guess. plugs sometimes need to be changed after flooding)

Go48

Actually, the color is probably a little more like a light tan, but yes it is the residue from the combustion process. You also will see that same thing, maybe not as much, on boingers that don't burn any/much oil during the combustion process, so it's not necessarily just oil combustion residue.

BTW, this material on the body of the plug has little effect on the efficiency of the plug since at this state the material is essentially non-conductive. In fact, what you look for in a properly running engine, that is, good air-fuel mix and a strong ignition, is a light tan material on the center ceramic insulator. If the center insulator is black, particularly shiney black, you have a problem one or more of those parameters, or with too much oil in the combustion chamber.

mazdaexe

Center insulation? that is like the tip in the middle? I will try to get a better pic tonite. I cant tell whether there is black stuff stuck around it.

Go48

No, the metallic rod in the center is the electrode. The ceramic insulator surrounds that and isolates it from the metallic body of the plug. See the attached image.

If the insulator is fouled with carbon material, the electrical energy in the center electrode will have difficulty jumping the gap to the electrode attached to the body of the plug and to produce a strong spark. In fact, it may not spark at all. Essentially, the electrically-conducting carbon material tends to short out the center electrode.

mazdaexe

Err... ok thanx.. now how do we check if the ceramic insulator is clean?

Go48

The ceramic insulator surrounds the center electrode. Look down into the inside of the plug to see the insulator around the electrode. (In the drawing, it's the gray material.) In a new plug, the color of the insulating material is white. If it accumulates incompletely-burned carbon material (like black stuff) on it, the plug will become fouled.

So, if the insulator is black, you must somehow clean the black material off in order to improve the performance of the plug. That can be very difficult unless you have a spark plug cleaning device that actually sand blasts the material off the insulator. Best to just replace the plugs if there is a lot of black material on there.

mazdaexe

ic. I guess mine is stuck w/ black stuff down at the electrode.
Thanx Go48 for the info!

Go48

Doesn't matter if the electrode itself (i.e., the metalic rod protruding from the insulator) has black on it--just the surrounding material.

You're welcome.

TeamRX8

iTrader: (25)

nope, mine's never flooded

Limey

I have 40K miles on my 2004 6 speed. I have yet to change the plugs, but really have no problems. Should I change anyway? Also, would I be right in stating there are 4 plugs, two inlet and two outlet?