I respectfully disagree with your general statement "most sensors are not the problem." The older single wire O2 sensors become lethargic at approx 60k miles. The frequency of the O2 sensor signal begins to taper off at 60k, at 90k it simply needs to be replaced because the switching time is too great. Here is one very good reason to replace the O2 sensor every 60k on the older KE-Jetronic system-fuel is >$3.00 a gallon. The KE fuel injection system was not that efficient to begin with so a fresh O2 sensor that switches rapidly definately helps the wallet and the emmisions.

Most of the cars that I have been involved with that have had bad tailpipe emmisions here in Califonia had high NoX on their initial test. After installing new O2 sensor's and reseting the fuel mixture on the greater majority of those cars...they passed with flying colors. The O2 rule applies to either the KA-Jetronic system (Frequency valve) or the KE-Jetronic system (EHA on fuel distirbutor)