Hi CarTalk gurus,
I need some plain-English advice. MUCH obliged in advance for any pointers!
1995 Honda Civic CX failed smog, with a NOx reading that was 2x the California limit. There have been no error lights that I have ever seen, although even my “low gas” lamp doesn’t turn on, so who knows. There’s also been a drop in gas mileage from about 325 miles/tank to 250 miles/tank in the last two years.
Is a Diagnostic Trouble Codes (DTC) check going to help, or are the errors likely to be too vague?
When it’s high NOx and no error codes, what’s the likely culprit? Sparkplugs? Wires? Distributor cap and rotor? O2 sensors? Catalytic converter? I’ve never touched any of the above in the car in the years I’ve owned 'er. (I have to plead ignoramus when it comes to maintenance, and need to learn more about maintenance schedules.)
Can I safely go “generic” with any of these, or is it vital to go OEM with any of the above components?
By the way, this is a system with 2 O2 sensors. The Honda dealer told me that the top-of-engine O2 sensor for the 1995 would cost $200 (which suggests he thinks it requires a full-spectrum O2 sensor), but friends are advising me that a generic 2-wire O2 sensor would be a small fraction of that. I’ve read forum posts where replacing the O2 sensor causes new problems: 1) Stripping the threads, 2) New check-engine lights (“ECM’s don’t like generic O2 sensors - best to go OEM”), 3) Severely failed smog readings.
Finally, what’s the best rust-buster compound to try on fittings like the O2 sensor? This car spent too long in Vermont winters before coming out to sunny California.
Thanks a million!