Took my mitsubishi through CT emissions 4 times and failed everytime on nox only, my numbers dropped a little everytime with repairs until i put the new egr valve on then my numbers shot up higher then they were in the first place and now i'm not sure what to do. new plugs new wires distributor and cap and router tryed the gas additives air filter evap canister cant afford a new cat so any help would be greatly appreciated.
Test One HC 103 CO 0.37 NOx 1891
basic tune up plugs wires air filter distributer cap, router then took
Test Two HC 91 CO 0.40 NOx 1876
tried the gas additives heet fuel injector cleaning etc.. then took
Test Three HC 96 CO 0.43 NOx 1761
replaced egr valve then took
Test Four HC 97 CO 0.42 NOx 1965
You need to check the oxygen sensor. You car may be running lean and therefore giving you increased NOx levels
Change the lambda/oxygen sensor in the exhaust.
The only other thing to bear in mind is that because your car is later than1991 the it is fitted with a three way catalytic converter, this monitorsall three gases and one can be affected without throwing all three out.
By the sound of the list of work that has either been checked or changed I would be looking at the Cat.
Has your head gasket gone and been fixed in the past year as this can cause the NOx to be higher than the rest, due to the antifreeze getting into the exhaust system and causing long term damage, just a thought.
Hope it helps and goodluck.
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Please note that while a failed catalytic converter will contribute to high NOx readings, the failure in itself may have been caused by some other upstream performance problem. In all cases, it is crucial to identify the root cause of the problem before blaming the converter.
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Was told that the sensor was not bad or I would have failed on the co and hc as well.. I only failed the NOx
co emissions too high for mot
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