I have a 1995 GMC Jimmy, with the 4.3 liter, 6 cylinder (Vortec) "W"
engine. It is running rich and gets only 6 miles per gallon. I found the
3 sparkplugs on the passenger side fouled with carbon, while the 3 plugs on
the driver side have normal wear. What is the most likely cause of the
problem? Any ideas will be most welcome.