Check compressions, replace plugs, if one or more are very black and sooty you will have a miss fire on the cylinder due to excessive fuel. (Leaking injector) faulty spark or low compression, is the coolant level low? If the plug looks a dirty rusty colour you may have a coolant leak into that cylinder, the white smoke is also a sign of coolant burning.
SPONSORED LINKS
Saturday, November 26th, 2011 AT 2:37 AM