Black 'n' White Spark Plugs

[matty_gti 20]

When i went to check my spark plugs today i relised that there all black (dry black carbon i think, not oily) with the electrode black and the just the little arm that goes over the electrode has a white tip?. i know that the running on the car is down to this but what?, Any ideas?.

 

P.S in the book it said 17NM to torque up the plugs, seems a bit tight?

[notamondayfan 44]

have a look in the bk of ur haynes manual, theres page or two on spark plugs.

[Ahl 4]

17NM isn't tight at all, its literally just 'nipping' them up.

 

The haynes manual does have a good selection of pics at the back. Ideally you want the electrodes to be a whitey-brown colour.

[Bassman 1]

If they have carbon deposits then it is probably running rich and your fuel economy will be suffering.

[Rob_the_Sparky 9]

It isn't that easy as the mixture can vary across the rev range, and particularly different when cold and at idle. I've had perfectly brown plugs while running 6.5% CO at idle!

 

It is an indicator but black carbon plus white tips is an interesting combination...

 

Rob

[Bassman 1]

It isn't that easy as the mixture can vary across the rev range, and particularly different when cold and at idle. I've had perfectly brown plugs while running 6.5% CO at idle!

 

It is an indicator but black carbon plus white tips is an interesting combination...

 

Rob

 

Probably still worth getting somebody with a gas analyser to test it and adjust the mixture as necessary. Especially if you have a "Boost Valve". When I bought my GTi it had an FSE Boost Valve fitted and it was set up to run far too rich. It is much better now, can even get 30mpg on a long run (with a following wind!).