I have a high mileage 95 Explorer which I now only use for biking and camping trips. These trips usually take me through the mountains of Colorado. Lately and consistently the check engine light has been going on and off as I drive through the mountains making significant elevation changes. However, once I'm at my destination or at home the light stays solid off and the engine runs smoothly. During the times the light is turning on and off the engine runs slightly rough. From what I understand the computer is making adjustments to the fuel mixture during elevation changes based on the sensor imput from the MAF in the upper intake manifold and the Hot O2 in the exhaust pipes. I think there are three Hot O2 sensors in the exhaust system. All of these sensors are the original. I'm thinking one or more of these sensors is now marginal. My question to the group is can I eliminate the on/off of the check engine light during elevation changes by changing one or more of these sensors? When the vehicle was newer the check engine light never came on. However, I can now reliably predict when the check engine light will start coming on based on where I am driving in the mountains. I know there are voltage measurements that can be made to the sensor outputs. However, when I am at home the light never comes on so I am assuming the sensor outputs are all in a normal range.
Thanks in advance for any input on this subject. Mark