Can faulty spark plugs cause a 1997 Nissan Altima not to pass a smog check?

Answer 1

This information provided by http://www.smogtips.com Definitely. Absolutely! What causes high HC? Fuel distribution to your engine's combustion chambers is controlled by your vehicle's ECU(Engine Control Unit) and fuel injectors. In order for your engine to pass a smog inspection, fuel delivery must be preciously controlled to produce the least emissions. If the injectors do not present enough fuel to the combustion chambers, this would cause low CO emissions. In a situation where the injectors present too much fuel, this would causes high CO emissions. In order for the ECU to estimate the right amount of fuel to distribute, it needs to know how much fuel is currently in the system. This way it can always maintain a proper Air/Fuel ratio and keep emission levels at their lowest. The main component responsible for letting the computer know how much fuel is in the exhaust system at this moment, is the Oxygen Sensor. The Oxygen Sensor sends an electrical signal to the ECU, letting the computer determine exactly how much fuel it should continue to deliver to the combustion chambers. If for any reason the 02 sensor (oxygen sensor) does not send accurate information to the computer or it is "lazy" in sending the correct signals, the fuel delivery program can be altered. The computer may then present either too much or not enough fuel to the combustion chambers and therefore cause an emission failure. In a computer controlled engine such as this, there are several components which also play a role in determining Air/Fuel ratio also. Along with the Oxygen Sensor, components such as the, TPS (Throttle Position Sensor), ECT (Engine Coolant Temperature Sensor) and the MAP (Manifold Absolute Pressure Sensor) sensors also send vital engine information to the computer which is used to determine proper air to fuel ratio. If any one of these components are defective they can alter the fuel delivery program. A smog service station can diagnose each component and report it's condition. High HC is normally caused due to improper spark delivery. During the combustion process any number of engine conditions can cause emissions failures. However because of the fact that out of the three systems your engine relies on to produce combustion (Air intake, Fuel Distribution, Spark Control), the Spark system has the highest likelihood of becoming defective sooner then the rest of your engine's due to the fact that sparkplugs and spark wires are constantly exposed to high temperatures and high voltages. You must insure your engines ignition system is functioning properly, by inspecting all sparkplugs and their wires. If any of the plugs look worn out or have excessive carbon build-up replace them immediately. You may use any brand of product designed to work in your vehicle. Most of the time aftermarket parts (non-factory) will be much cheaper. More then likely you will see an instant performance increase once these corrections are made. GET MORE INFO AT: http://www.smogtips.com