There are several reasons why your Mercury Sable could have produced high
NO. The most common is your Mercury's EGR system. The EGR valve in your
Mercury Sable is responsible for re-circulating a small amount of exhaust
gas back into the combustion chamber. This is done to cool down the chamber
temperature by producing an inert gas along with the regular fuel mixture.
Nitrous Oxides emissions are formed when engine chamber temperatures rise
above 2500* F. Keeping the chamber cool reduces NOx emission.
The second most common cause for high NO are lean fuel mixtures. A lean fuel
mixture is when the engine receives less fuel then is necessary to obtain
efficient combustion. Lean fuel mixtures are often due to vacuum leaks or
defective fuel control. A smog check repair shop will have to ensure your
Mercury Sable is in proper fuel control. They will have to inspect the fuel
injection "feedback" system and ensure the engine computer is sending the
correct signals to the fuel injectors to either increase or decrease fuel
delivery to the combustion chambers. When the engine doesn't get enough fuel
NO emissions are increased.
