Jaguar Repair: FUEL, tail pipe, mechanical problem

Question
Howard
can unbured gas go through the vales. and still the plugs look as if their burning clean And no black smoke from the tail pipe

Answer
Hi Howaed,

By "Unburned" gas going into the exhaust do you mean on an "HC" test? Yes, on an exhaust analyzer you can see high HC and not see it show on a plug nor black smoke out the tail pipe.

This is often the case when a test shows high HC and correct CO on a test. High HC is usually an electrical or mechanical problem and CO is mixture. However when the mixture is very rich it will show high HC and high CO. This condition will often show black smoke out the tail pipe and flat black on the plugs.

Howard