How come my plugs get a build up of carbon so quickly?

The car runs perfect on new or cleaned plugs, but after a week you can tell it's not perfect anymore, and voila, plugs have carbon build up.

I've cleaned them with Marvel Mystery Oil and some gentle filing, and have had great results - the car runs perfect for another week.

How do you prevent this?

 

Myaber your MOP is on 100% ?

Try disconnecting it and running FULL pre-mix for a week after you clean the plugs. If the build up is gone that was your problem. If not then ummm....fuel filter problem?

 

Whats your setup? NA or TII? Running rich possibly?

 

Sounds like you're running rich. Black deposits? Change your air filter, your fuel filter, and have your injectors purged or ultrasonically cleaned. That should take care of it

And oh yes, check for any codes, an O2 sensor will cause your car to run very rich (it did to me), as will a faulty TPS, AFM, Water thermosensor, or IAT sensor.

Good luck!
-Ross

 

It is a TII, stock. I've done the following recently:
-fuel filter
-plug wires & plugs
-MMO premix
-air filter
-belts

Fingers will checking for codes lead me to problems with O2, TPS etc? I have the TPS lights which I think I can use to check for codes? I've never done that before.