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Failed Smog Test
 

1990 Acura Integra Failed Smog Test High NO

My Acura failed the NO (PPM) on a smog test with a MEAS of 1015. The car is throwing no codes on the computer what can be causing this?


Answer:  

Your Acura Integra could be suffering from a high NO fault caused by a defective EGR valve. We recommend having your Acura Integra's EGR system inspected for proper operation.

You should first make sure your Acura Integra is getting vacuum to the EGR valve. Next manually open the valve while the engine is at idle and check for engine idle drop. Be careful, the engine will be hot. Your Interga should stall or come very close to when the EGR valve is opened. This will indicate the EGR passages are free and clear from carbon buildup. If no RPM drop, the passages are plugged and need to be cleaned. If there is idle drop then look into why the EGR valve might not be receiving manifold vacuum required to open the valve during part-throttle and light load. The Acura's EGR valve is computer controlled via the EGR solenoid. The solenoid should feed vacuum to the EGR valve when off idle and under slight load.

Other reasons your Acura Integra could be producing high NO include: Bad engine cooling, lean fuel condition and/or high mileage (carbon buildup).

Bad Engine Cooling - If your Integra has cooling system problems chances are excessive NO is being created. NOx (Nitrous Oxides) is created when an engine's combustion chamber temperatures reach over 2500F. A bad cooling system will create NOx.

High Cylinder Compression - Carbon build-up within your Acura's engine combustion chambers will cause increased engine temperature and high NOx. Carbon build-up causes increased cylinder compression, which causes high temperatures, which result in high NOx emissions.

Lean Fuel Mixtures - Lean fuel mixtures cause high NOx also. 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 and/or defective emission sensors which report air/fuel mixture amounts to the ECU. A good example of such component(s) is your Acura Integra's oxygen sensor.


posted by SmogTips Support 01-12-2015 05:28 PM
 


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