Vibration with Check Engine, Trac Off

[ajprobashi]

Ok, here is the problem. I have a 1999 ES300. Bought it used. Around 122k miles. Everything is fine except the check engine light and the traction light came on. On top of that the car staretd to vibrate a little bit when I started the engine once. I turned my car off and started it back up again and the vibration stopped. While the car was vibrating the check engine light was blinking and once the vibration was gone the check engine light stayed solid.
I went to autozone and got it checked, and it gave me a code regarding O2 sensors. Now I changed only one sensor however, I'm guessing the other 2 sensors needs to be replaced as well. Would a car vibrate if it had faulty O2 sensors?

[jdmccright]

There are three O2 sensors: 2 located before the cat (one for each cylinder bank, placed in the exhaust downpipes) and one post-cat O2.

I presume the diagnostic code told you which sensor was at fault...it has that capability. Ideally all three should be changed, especially if you change brands, but technically they should all perform within OEM specs.

To answer your question, yes a faulty O2 can cause poor idling and poor fuel economy. They detect the amount of unburned hyrdocarbons (fuel) in the exhaust stream and use that to adjust the amount of fuel injected into the cylinders according to your driving state...economy, performance, etc. This is to maximaze fuel efficiency and minimize pollution. When one goes bad, particularly one of the pre-cat sensors, the ECM has to resort to a set of pre-determined fuel/air "maps" to compensate, resulting in engine inefficiencies. hope this helps!