I had the dealer change my plugs and do a compression test while I had it in for an oil change (got hosed on the plugs, but that's another story).
I got the car a few months ago, and wanted a baseline to go from.

I had them return the used plugs to me, and have the photos attached. Do these seem to have excessive carbon build up on them? I know it's an issue on these cars, but I have not seen plugs that looked like this before (previous car was a turbo 4cyl). Excessive or normal?
These are the stock plugs (as far as I know). The car is an 04 6spd with 44,500km on the odo [approx 27,650mi]


FYI
compression came out 7.6, 7.6 and 7.7 kgf/cm^2 on the front rotor
and 7.5, 7.6 and 7.5 kgf/cm^2 on the rear.
Std value is 8.5 and minimum is 6.9, so it's a bit low, but at least consistent across all readings.

WOW! that is dirty. how many miles those plugs got on them?

Yeah, Looks like youre running alittle rich or you premixing too much oil?

The threads looks oily?

Only owned the car since September. Mileage is listed in the original post [27,650mi].

I haven't used pre-mix or synthetic or anything like that yet, thou I plan to. I try to take the rpms up each trip, and my drive to work isn't that short (30 min or so) so I don't do a lot of short trips.
When I checked the history of the car, Mazda said all recalls were performed without issue. Is there an engine flash that wasn't a recall that I might not have yet?

The high carbon is the main reason I was looking at the Amsoil Interceptor pre-mix instead of the Saber (see recent posts in the pre-mix sticky). It says that it has a lot of anti-carbon build up additives.

My best guess is that the previous owner did not run the engine up to burn off excess carbon, and it just accumulated. As for the oil on the threads..??? The deposits on the spark plug are dry (powdery) not oily.

those compression numbers are actually pretty good, it's not how high they are, it's how even they are, and frankly that's damn consistent for all sides and both rotors.

now rev that bad boy and keep it healthy!

Only owned the car since September. Mileage is listed in the original post [27,650mi].

I haven't used pre-mix or synthetic or anything like that yet, thou I plan to. I try to take the rpms up each trip, and my drive to work isn't that short (30 min or so) so I don't do a lot of short trips.
When I checked the history of the car, Mazda said all recalls were performed without issue. Is there an engine flash that wasn't a recall that I might not have yet?

The high carbon is the main reason I was looking at the Amsoil Interceptor pre-mix instead of the Saber (see recent posts in the pre-mix sticky). It says that it has a lot of anti-carbon build up additives.

My best guess is that the previous owner did not run the engine up to burn off excess carbon, and it just accumulated. As for the oil on the threads..??? The deposits on the spark plug are dry (powdery) not oily.

the plugs look well pampered, not good.. i would say flog the hell out of them, but my guess is you replaced them..

so flog the hell out of the new ones..


beers :beer:

Only owned the car since September. Mileage is listed in the original post [27,650mi].

I haven't used pre-mix or synthetic or anything like that yet, thou I plan to. I try to take the rpms up each trip, and my drive to work isn't that short (30 min or so) so I don't do a lot of short trips.
When I checked the history of the car, Mazda said all recalls were performed without issue. Is there an engine flash that wasn't a recall that I might not have yet?

The high carbon is the main reason I was looking at the Amsoil Interceptor pre-mix instead of the Saber (see recent posts in the pre-mix sticky). It says that it has a lot of anti-carbon build up additives.

My best guess is that the previous owner did not run the engine up to burn off excess carbon, and it just accumulated. As for the oil on the threads..??? The deposits on the spark plug are dry (powdery) not oily.

27k is getting up there for 8 plugs. Thanks to the recall and some hard starts the dealer has been changing mine every 12k :)

Look into Idemitsu premix.

Damn ...

Its time to drive it like you stole it.

the compression seems fine. its not very good. but its ok.

Might want to look into premix, I use Idemitsu right now.

The center is light tan, which is what you want.

The rest of th eplug gets black like that from sitting at idle too long. DD driving.

What was the RPM's of the test? You might want to change your Air Filter, get some more air in the engine and run leaner and cleaner. Here are mine...

http://www.rx8club.com/showthread.php?p=2153320#post2153320

For comparison here are my plugs
http://www.rx8club.com/showpost.php?p=2154248&postcount=1

Not sure what the RPM was during the compression test. The work order said it was a compression test as per the recall test for engine replacement. I'm hoping the Mazda dealer ran it at the correct RPM, and/or has the equipment to measure and compensate for the actual speed.

Thanks for the additional photos. It looks like the car was probably being babied. I'm going to be getting a new filter and babying it wont be an issue with me driving, so hopefully when these new ones come out they'll look a little better.

BG44k

You know this is the 2nd time I have seen some bad plugs like that. That last one I seen was from that dude down under, I cant recall his name, I think its Taka.
I'm about to change mine. I wonder what they will look like.
-Gil

I had the dealer change my plugs and do a compression test while I had it in for an oil change (got hosed on the plugs, but that's another story).
I got the car a few months ago, and wanted a baseline to go from.


FYI
compression came out 7.6, 7.6 and 7.7 kgf/cm^2 on the front rotor
and 7.5, 7.6 and 7.5 kgf/cm^2 on the rear.
Std value is 8.5 and minimum is 6.9, so it's a bit low, but at least consistent across all readings.
I strongly suggest you find out what RPM the motor was turning over before you make a call on how good the numbers are. The higher the RPM the higher the compression ratio will be.
Find out the RPM's and use the chart attached.
Railton

Dont mean to hijack, but anyone know the cheapest/best place to get plugs/coils?

Im on that 27k mark on both right now, idle has gotten a bit rough, and needing to replace them to see if thats the issue or motor mounts for the 2nd time.

Here is a Post with ideas. I got on E-Bay...
http://www.rx8club.com/showthread.php?t=107791

Dont mean to hijack, but anyone know the cheapest/best place to get plugs/coils?

Im on that 27k mark on both right now, idle has gotten a bit rough, and needing to replace them to see if thats the issue or motor mounts for the 2nd time.

sparkplugs.com for the plugs

and

onlinemazdaparts.com for the coils

pics are kind of far away, they look like your running rich or the plugs are fouled.

I think they look awful...

Can you feel that your 8 said thank you to you? Just right after you took those out :lol:

Im about to do mine. oh crap I forgot to order trailing plugs. Sparkplugs.com here I come !

I think they look awful...



How many miles? Did you change your air filter? What type of driving do you do?

Short trips? Give us some more info please....

http://www.mazsport.net/store/index.php?l=product_detail&p=23&added=23
Would these NGK spark plugs be a good replacement for my 8? it has 44000 and I can bet they haven't been changed a good while.

http://www.mazsport.net/store/index.php?l=product_detail&p=23&added=23
Would these NGK spark plugs be a good replacement for my 8? it has 44000 and I can bet they haven't been changed a good while.

Those would work for about 20K miles...they are not the correct OEM plugs.
The stock OEM plugs that are recommended and installed in new RX-8 are these NGK ones on the bottom of the page and should have no problem going 30K miles...

http://www.sparkplugs.com/results_app.asp?productTypeID=1&AAIA=1416844