Hi,welcome to Just Answer.I will be happy to assist you with this question today.I will try and assist you as best as possible from here,feel free to ask any follow up questions to my info provided here.
If your check engine light has come on with this fault as well then the fault codes need checked to see what codes are set and then corrected and this may correct this fault here.
If the light isnt on if your engine air filter is dirty then it is possible that this is the cause as well as a dirty mass air flow sensor as well which can be cleaned by purchasing some mass air flow sensor cleaner from a local parts store and then removing and cleaning the sensor then reinstalling it.
There is no check engine light on.
I have also seen oxygen sensors (before the catalytic converter) read incorrectly and cause this issue as well.I usually recommend having the sensor replaced at around 100,000 miles to ensure it is operating properly.
If your catalytic converter isnt operating efficiently then it will also cause this and may not set a fault code either.I would start with the air filter and cleaning the mass air flow sensor and then also possibly replacing the pre cat. oxygen sensor.
That sounds like a good first step...i can take it back through etest as many times as I want. So get a new air filter, cleAN MAF, THEN MOVE ON TO THE O2 SENSOR if those things fail.