I yanked my plugs the other day to check them after 20k miles, and EVERY SING LE ONE had a fine layer of white deposit all over the electrodes. It came off easily, even with just my work gloves. The guys at AutoZone said that that meant I was running lean. Thoughts? Ideas?

Also...

Denso's website site says the correct iridium plugs for my car are IK20, which is what I'm running now. But when I cross-reference the NGK plugs for our car using the tool at http://www.spark-plugs.co.uk/pages/p...partsearch.htm, it says the corresponding Denso Iridium plug is IK16 (hotter plug). Anyone have any ideas why?

 

Any reason you aren't running the factory recommended NGK platinums? or the other alternative, NGK V-power coppers?

 

Because I tried them and they worked great....?

 

iridiums are only for boosted aplications. just save the money and go by your self some ngk coppers, 11 buks for all 6 at pep boys

 

Guys... let's not turn this into a "what spark plug should I buy" thread. I already have the Densos, so unless someone can tell me exactly why my spark plug choice caused the deposits, the argument is pointless.

Any opinions on the heat range thing?

 

Umm that actually sounds normal.
If they were yellow and glazed you'd be running lean and hot.
To rich would be very dark.
Tan to white is a nice clean burn for a plug with 20K on it.

To add to that the fact that the white deposit came off with a simple wipe with something soft sounds even better.

I don't know what your concern is?

 

Phew! Thanks for clearing that up. The Autozone guys had me a little worried.

I asked Denso about the heat range thing. Hopefully they will get back to me.

 

If all 6 plugs had it I would say it was normal but if it was only the 3 on the back side then it could be a fuel distribution problem. It's not a big deal unless you noticed lower performance or knock. Also check for codes like an injector or something. There is a sticky in the boosted forums that talks about modifying the fuel rail so that the back side doesn't run lean.

 

Thanks for the tip. You know, I did notice that the front 3 plugs needed to be re-gapped but the rear 3 didn't really.... Cause for concern?

 

Just make sure they are gapped correctly if they are not, with a plug like iridium I don't see why they shouldn't be but I guess anything can happen.

 

My plugs usually have a fine light white coating. And that reminds me, time to change plugs again.