My 1992 Honda Accord failed the emission test today for a too high NOX reading. The applicable standard is 2.50 and my car’s reading was 2.61. I’ve read that high NOX has something to do with a malfunctioning EGR valve. Will replacing the EGR valve guarantee that I pass the emissions test? I don’t want to start throwing money at all kinds of parts. Should I buy genuine Honda brand parts or are Standard Motor Products parts that are available on Amazon.com for a lot less $ as good quality get the job done? In case it helps, the Hydrocarbon reading was .60 and the Carbon Monoxide reading was 8.81.
High NO levels are usually the result of cylinder temperatures that are too high, and high cylinder temperatures tend to result from a malfunctioning EGR valve. Try simply cleaning the EGR, to see if that makes a difference.
High cylinder temps can also result from too lean a fuel-air mixture. A lean fuel-air mixture can stem from a bad O2 sensor, or even something as simple as a vacuum leak.
However, since a lean fuel-air mixture will also tend to give you high Hydrocarbon readings, it is more likely that your problem is EGR-based.
Don’t think of the EGR as a “part” (the valve). Think of it as a system with the valve being one part of the system. You need to figure out how the EGR system works on that car and figure out how to check the whole system - not just the valve. A repair manual will be handy - or use the internet.
If you do have an EGR problem, cleaning is often a remedy.
Thanks for the suggestions. I’ll try cleaning the EGR valve and ports. Since I have to provide a receipt for work done and I can’t really get a receipt for doing my own cleaning, is the O2 sensor the least expensive part I could replace and get a receipt for that would help the situation?
Also check if the EGR valve vacuum control solenoid is working. This solenoid is controlled by the computer and applies vacuum to the EGR valve when required.