There are several reasons which could have caused your Mitsubishi Lancer to produce high NO. The most common fault which causes high NOx is a malfunctioning EGR system.
NOx is created when an engine's combustion chamber temperatures reach over 2500F. The EGR system, including the EGR valve, help lower NOx by delivering the combustion chamber inert gas (exhaust) in order to cool down combustion temperatures.
High NOx can also be caused by excessive carbon build-up on piston and valve heads, engine overheating, and vacuum leaks.
Our recommendation is to have your Lancer looked at by a professional smog check repair station. They will charge a diagnosis fee (usually 2 hours of labor) and they will be able to tell you exactly why your Mitsubishi is failing the smog check because of high NO.
posted by SmogTips Support
