Carbon Build Up

[scirocogtx]

I have a problem with excessive carbon build up on all of my spark plugs. I understand this is normally caused by running the engine too rich or if the timing is out.

However this is where the problem lies.

I have set my timing to 6 deg Btdc as marked on the flywheel (1.8i DX 8v), have replaced the plugs, leads, rotor arm and dizzy cap within the past two weeks. I have checked the air filter and it is not overly dirty (K+N), have replaced the Warm Up Reg (thanks Markh) and the aux air valve. I have checked the compression on all of the cylinders and they are all showing good equal figures of around 180psi.

Now as the WUR has just been replaced can this being previously faulty cause carbon build up? Maybe supplying too much fuel as might have been stuck in cold mode?
Or should I start looking at my fuel mixture?
Or something else?

I understand that adjusting the fuel mixture, according to haynes, is done using a long thin screwdriver down hole in air meter. If I am going to adjust this how much do I need to screw it for it to make a difference?

Thanks

[scirocogtx]

Have since adjusted the mixture and my carbon has cleared up.
However I probably turned it too far, it only needs a very small amount of turning, and my plugs will maybe overheat now.
I will run it for a day or two and check the plugs to see if colour changes and if so I will adjust co level.

Am glad that this is the problem and since turning the mixture screw my car starts a lot better now.

[D-reame]

You can cause a lot of damage to the valves if you are running too lean. Take it to a MOT station or a garage with a air sampler. This will set it up correct. Also if you are running the car at idle for long periods and are not driving the car under normal conditions this can lead to the plugs fowling up. Give it a good blast once you have had it set up. It should clear them.

[scirocogtx]

Am trying to get hold of a local garage with an exhaust gas analyser as an MOT station will just give me a printout rather than an immediate figure that can be adjusted in situ.
Not a lot of garages still use that kind of machine as there is not the demand for them anymore.
Will have to delve further.

Have adjusted mixture so that carbon has returned and will work in short increments from there. I'd rather the cylinders ran too cold than hot as, like you stated, I don't want to damage valves etc.

[Nate]

most mot gas analysers will give an immediate readout on screen for adjustment. try sesrching for garages that do a crypton tune