Having problems with your 1997 Nissan Maxima ?

HC & CO% emission

\015 I have Nissan Altima 94, GXE, and it has been faiked for HC and CO%. I have changed spark plug and distributor cap, roter and still did not passed. Please advise? Is the Oxygen Sensor needs to be replaced?You help will be greatly appreciated.PK\015 Posted / edited by AnonymousUser on : 21-01-2019

Answers :

Prabhatk8: I am going to run several things by you, OK?
\015\0121. If the oil and filter have not recently been changed, it is possible that the high readings are a result of what has collected in the crank case and is being drawn up through the PCV. The contamination is enough to fail the emissions. You did not mention the numbers, so I can only offer suggestions, starting with the simplest solutions and continuing on with more complex solutions.
\015\0122. The Ignition timing being advanced can cause the condition you have described, to a certain degree. However, the HC readings, are these being taken at an idle and at above 2,200 RPM ?
\015\0123. Nissan also dated their plug wires. If you look at the wires closely, the outer insulation should have the year the wires were manufactured. The insulation is marked about every 6 inches or so. Old wires can cause agrivate a problem like you have.
\015\012If the car has the factory wires, they will either have the name "Yazaki" or "Sumitomo" on the wire insulation. These are excellent quality wires! If you decide to replace them, either replace them with the factory (dealer supplied) wires or ones made by NGK.
\015\012I have found nothing equal to them in performance and longevity.
\015\012Don't go cheap on the ignition parts! Too much of an air gap between the cap and rotor will raise the HC level. Excessive gap on spark plugs or weak spark will also create the condition.
\015\012The oxygen sensor can cause the problem, however, don't just replace it because you suspect it may be bad. The part can be tested, but you may not be equipped to do so. Check with Auto Zone or O'Reilley's. They have scanners. Some of these scanners have the ability to monitor the Oxygen sensors in "Real time". Which means looking at them functioning while you are standing there. The sensor is actually a voltage generator which generates milli volts based off of the exhaust passing over it. The more or less oxygen that is present in the exhaust, changes the voltage values which in turn is sent to the ECM to adjust the pulse width of the injectors , keeping the CO and HC within certain parameters.
\015\012Technically they refer to it as a "Lamda Window".
\015\012(Lamda, Lambda, Lambda and Omega Moo!)( I couldn't resist! For those of you who saw the movie the Revenge of the Nerds)
\015\012Sorry...where was I.?.........
\015\0124, A false air problem can cause this symptom depending on where the leak is. Check for a small crack or leak in the boot which connects the air mass sensor with the throttle body.
\015\0125. The Altima's among other Nissan's had problems with condensation dripping down on top of the ECM's connectors where they plug into the ECM. When they got corroded, this would affect the performance , including EMISSIONS.
\015\012PK, I hope this will give you some direction to go in. If the numbers are "real close" In all likely hood, if you change the oil and filter just before you go for the test, you will probably pass.
\015\012Tell me what the numbers are, including th e "NOX" figures.
\015\012I I know what these are, I can help you more easily. What I am doing here is shooting in the dark!
\015\012Good luck and let me know if I have done you any good.
\015\012P.S. If you un-plug the connectors at the ECM and they are corroded, there are cleaners you can buy from Radio Shack and the local automotive parts houses. One is for cleaning and neutralizing the corrosion and the other is a dialectic grease which you apply to the connectors afterword's to keep corrosion from coming back.
Repair Help & Product Troubleshooting for 1997 Nissan Maxima

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