Fouled plugs can really be a problem on high mileage waterboxers, and on
any engine that does mainly short trips.  I recently had my '84 in the
body shop for two weeks where they drove it in and out of various areas
repeatedly.  When I picked up the van it was running on two cylinders!
I was ready to sue for a new engine until I checked the plugs, two of
which were fouled.

Oil draining down on the cylinders after shutdown gets past the worn oil
control rings on cold start-up for one thing, but I remember reading
somewhere that there is design feature that causes problems with many
engines built in the 1980's.  On cold start the computer defaults to a
pre-set default rich setting that was calculated for minimal emissions
in the 1980's with 1980's gas formulation taken into account, and does
not adjust to proper mixture settings until it gets information from the
sensors that the engine has warmed up.

Apparently our current gas formulation (lower actual "heat content")
ends up in effect resulting in an overly "rich" incomplete burn in the
cold running condition because of this default setting from the past,
and that can lead to plug fouling if the engine is not warmed up each
time it is driven.

Anybody else ever hear of this theory?

--
Stuart MacMillan
Manager, Case Program
800-909-8244 ext 208

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