Spark plugs fauling when running idle

EdHut · 08-29-2001, 03:09 PM

Hi all,

The spark plugs in my 1966 911 tend to faul up when the engine has run idle for a while, for example when driving in slow traffic and waiting for traffic lights. The engine will gradually start to run very rough, with at least one cylinder misfiring.

As soon as the engine runs higher rpm's again the problem lessens, because the plugs get burned cleaner again, but in the longer run the plugs have to be cleaned to get a engine running really smooth again.

My mechanic says that it is quite normal that the plugs get faul when running idle.
Is he correct, or is there something wrong with my engine and/or carbs (Webers) and/or whatever?
Is the mixture too lean or rich?
The engine has about 140K Miles on it, but does not use much oil at all.

Thanks in advance,
Ed

Early_S_Man · 08-29-2001, 03:19 PM

Ed,

Perfectly normal for all 911s prior to 1969 ... when the Bosch CDI-system was introduced. The obvious, and simple answer is a retrofit of the Bosch CDI-unit and coil! Used systems are available and work fine!

------------------
Warren Hall
1973 911S Targa
1992 Dodge Dakota 5.2 4X4 parts hauler

EdHut · 08-30-2001, 10:45 AM

Warren,

I'm relieved to hear that it's normal for this to happen.

Can you explain what the essential improvement of the CDI unit is? As far as I can find out so far is the higher voltage and thus better spark. Are there other reasons as well?

Thanks,
Ed

EdHut · 08-30-2001, 10:48 AM

Warren,

I'm relieved to hear that it's normal for this to happen.

Can you explain what the essential improvement of the CDI unit is? As far as I can find out so far is the higher voltage and thus better spark. Are there other reasons as well?

Thanks,
Ed