Spark Plug Colour

[Bizarro]

Yesterday my car developed a misfire when accelerating in top gear from about 60/70 MPH. It is missing when doing a constant speed and when I accelerate it misses until the revs rise and then it clears.
The problem was particularly bad yesterday when driving on the motorway when accelerating and decelerating between 60 and 80.

Today I have taken out the plugs and the plug from number 1 cylinder is very clean and a bright colour as if it is getting very hot. The other 5 are a darker colour and have oil residue on them. Is this significant to the missing or is this normal? Plugs are Motorcraft and are set at .025"
I have ordered a new set of NGK plugs and plan to gap at .028"?

Plugs as they came out of the car (no. 1 cylinder top left)


Plugs from 1 and 4

[JLSELAN]

Reading spark plugs is a somewhat complicated topic so you might want to check out these sites:
http://www.ngksparkplugs.com/tech_support/spark_pl...

and

http://www.youtube.com/watch?v=IvWl-dUNUYg&fea...

Also, you really cannot get an unambiguous reading unless you start with new plugs and "cut clean" when you stop the engine.

[Bizarro]

Thanks for the pointers, ill take a look. What is meant by 'cut clean'?

[JLSELAN]

If you want a plug reading that indicates how the engine in performing under power, it is important to avoid having the engine idle before you shut it down. Of course that is difficult to do in street driving, but on a track the idea of "cutting clean" is to have the engine at, or near, full power, before you turn off the ignition, put in the clutch and take it out of gear. Then, ideally, you coast into the racing pits and pull the plugs to read them. Needless to say, it's a technique that takes a little practice .

Edited by JLSELAN on Saturday 29th May 22:28