What causes high HC (hydrocarbon)?
High HC is caused by incomplete combustion; in other words, the air and fuel that went in to the combustion chamber was not completely burned, now the unburned fuel has ended up in the tailpipe. Problems that can cause incomplete combustion include: • An ignition misfire. If a spark plug does not spark, the air/fuel mixture in the combustion chamber does not burn and then goes out the tailpipe. • Incorrect air fuel mixture. If there is not enough fuel in the combustion chamber to ignite, the fuel that is there goes out the tailpipe. • Low compression. If the compression is too low the air/fuel mixture will not ignite and the unburned fuel will go out the tailpipe. • A bad catalytic converter. The converter lives in the exhaust pipe and burns unburned gas as it passes through. What causes high CO (carbon monoxide)? High CO is caused by a rich air/fuel mixture. The air fuel ratio should be 14.7 parts air to to 1 part fuel. Problems that can cause a rich mixture include: • Problems with t
