Clean the MAF sensor and the IAC valve with MAF cleaner only...change your oil and filter, put correct air in tires and disconnect battery cable....wait 10 minutes, reconnect battery, turn off all accessories, lights, wipers, radio etc...put key in ignition and turn to the on position, BUT do not start...wait 1minute then turn off...turn on again and start car...do not rev, let car idle for 15 minutes, then go for a 20 minute drive. Before you take the car for another test, drive it for approximately 1 hour, both in the city and on the highway so the sensors can readjust....do not race or over rev the car...drive normally....cheers.
SOURCE: CHEVY SUBURBAN FAILED SMOG BECAUSE OF HIGH NOX VALUES.
nox is from running lean..... its realy high temps that cause this.......... replace the o2 sensors this should cure that any more help let me know
SOURCE: cant pass smog failed nox got 2032,allowed 695 95
Since your car has no EGR valve, you have one of two problems. You either have a bad O2 sensor, making the car run lean, or you need a new Cat. Or, you've had a bad O2 for so long that it ruined your cat, and now you may have to replace them both. Either way, I'd highly recommend having a smog tech take care of this problem for you, since you have no access to a smog machine that will tell you if the repairs you've done have solved your problem.
SOURCE: 2000 Hyundai Accent failed the emission test, high
Did you RESET the Adaptives?.. if you didn't that may be the problem. To reset adaptives, remove both battery cables and touch the cables together for 30 seconds (60 seconds is better), then reconnect the cables to the battery -- see if that cures it. You are correct, there is no EGR valve on that engine. However, there are several other sensors which could be causing your problem.. one is the MAF, the other is the MAP and still another is the IAT and the ECT (MAF - MASS AIR FLOW, MAP - MANIFOLD ABSOLUTE PRESSURE, IAT - INTAKE AIR TEMP SENSOR and finally the ECT- Engine Coolant Temp Snsr. If any of these sensors is malfunctioning,& lying to the ECM, they could cause a 'LEAN' fuel condition and that's why your NOx's are high.
SOURCE: 1992 dodge stealth failed smog test with high NOx
NOX is produced when cylinder temperatures exceed 2500 f.
Your vehicle has 2 ways to directly reduce NOX, EGR system, and catalytic converter, and also the cooling system indirectly.
Take a look at the EGR system, vacuum lines, pipes, and make sure the diaphragm moves. Disconnect the vacuum line, then push on the diaphragm and plug the hole (from vacuum line) when you release the diaphragm there should be vacuum. Also you may want to take it out and give the EGR passages and EGR valve a good cleaning, with some type of carbon cleaner like carb cleaner.
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