Re: filthy rich

["Melissa & Jim" <jadney@vwtype3.org>]

On 31 Oct 97, Steve Bradley wrote:

> Melissa & Jim wrote:
> > 
> > On 30 Oct 97, Steve Bradley wrote:

> > > When I pull my plugs, the electrodes on the ones on cylinders 1 and
> > > 3 are brown (which is normal, I assume) and the area directly
> > > adjacent to the thread, facing the combustion chamber is fluffy
> > > black (not normal, I assume).
> > >
> > > The plugs on cylinders 2 and 4 are totally carbon fouled, fluffy
> > > black on every part of the plug exposed to the combustion chamber.
> > >
> > > Does the CU or some other component send more gas to cylinders 2 and
> > > 4 for some reason?
> > 
> > There should be nothing special about 2 and 4.  This is pretty
> > strange.  The 71s are just about the best year.
> > 
> > Things to try/consider:
> > 
> > Check your compression all around.
> > 
> > Check your charging system voltage.
> > 
> > Check the timing and the valve adjustment.
> > 
> > How's your gas mileage?
> > 
> 
> Gas mileage is 20-21 in town (unknown on the road). Would low
> compression cause said symptoms? Timing and valves are OK.

Your symptoms are very wierd.  I can't think of anything that would 
cause this kind of a problem directly.  Thus I am guessing that you 
have some problem that tends to make everything run a bit rich (like 
low charging system voltage) coupled with some local problem that 
pushes things over the edge (the slippery slope) but just in two 
cylinders.  The only thing I can think of so far is poor compression 
(for whatever reason) in 2 & 4.

The routing of the plug wires for 1 & 2 can sometimes be a problem, 
but 3 & 4 are easy.  It is possible that the spark for 2 is sometimes 
getting shunted to ground; you should feel the miss that this 
produces, and your gas mileage would suffer.

Your gas mileage sounds pretty standard (and honest) so this adds to 
our quandry.  Have you tried changing all four plugs and seeing if 
the symptom reappears quickly.  It is possible that there is really 
no problem or that you just happen to have two mis-matched plugs in 
there.  Bosch W8AC is the right plug, W8APs also work well for more 
money.

Jim
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       Melissa Kepner                                    Jim Adney
                             Laura Kepner-Adney
                         jadney@vwtype3.org      
                             Madison, Wisconsin
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