I think I have to change the oxygen sensor on my BMW. Problem is i don%26#039;t know exactly what they do. In cold mornings the RPM keeps fluctuating and is very low, when it gets under 500 RPM, of course it stops. Someone told me the oxygen sensor might be the problem, not sure though. Thanks|||I doubt it. Depending on what year model it is..most O2 sensors do not start working until they reach roughly 600F. When they are hot enough then they send information back to the computer about the amount of oxygen in the exhaust stream. The computer then makes adjustments to run the car rich and lean to provide the needed %26quot;fuel%26quot; for the catalytic converter to burn up the excess hydrocarbons in the exhaust. I would think your problem either to be a idle air control motor malfunction or perhaps your intake air temp or coolant temp sensor is not functioning properly. Your best bet is to take it to shop to have it diagnosed because you can throw a lot of money at it without fixing the problem..|||The oxygen sensor on your car does exactly what the name implies: The oxygen sensor tests the exhaust gasses and determines how much residual oxygen is in the exhaust. By crunching some numbers, the computer then determines what the air/fuel ratio actually is based on what the oxygen sensor tells it. Pretty nifty, huh? Also called the O2 sensor, the oxygen sensor is a critical component in your fuel injection system. If your oxygen sensor isn鈥檛 operating properly, your computer doesn鈥檛 know the rate at which to inject additional gasoline. The end result is that a fouled oxygen sensor causes the engine to run rich, which can then lead to catalytic converter failure.|||o2 sensors monitor the exhaust gases allowing the computer to adjust the air and fuel mixture. If you have problems witha fluctuating and low idle in the morning, have the idle air control valve checked and have the throttle body cleaned out. A bad o2 sensor should not cause low or fluctuating idle.
good luck|||I agree with the inital diagnosis, but further inspection would need to be done. An oxygen sensor is wired to your computer and it regulates your air/fuel ratio according to exhaust conditions. Also a secondary oxygen sensor is usually located after the catalytic converter to monitor your emissions. I would venture a guess that your primary O2 sensor (likely located on or near the header/exhaust manifold) is the culprit for your issue. I don%26#039;t reccomend any %26quot;quick fixes%26quot; but I%26#039;d first check for proper connection and then consider swapping it out for a new one.|||I monitors the amount of unburned fuel/oxygen and adjusts the amount of fuel being injected could also be the mass airflow sensor usually located on the intake tube running from the air filter to the intake with the car running unplug it if no change thats it. hope I could help|||Air C is correct. The O2 sensors on your vehicle are not controlling fuel at cold startup, and do not operate until they have heated to the proper temperature. You have an intake air control problem or possible vacuum leak.|||I have an AUDI A4... and I thought it was the O2 sensor as well... same with the dealership. I spend a bundle on getting it replaced and it didn%26#039;t help at all. O2 sensors determine the proper amount of air to mix with the fuel... and so it possibly might be the sensor. What worked for my car... fuel injector replacement.|||It doesn%26#039;t have anything to do with your O2 sensor. Sounds to me that your idle control valve is going. What this does is controls the automatic choke (holds the throttle open) and when it doesn%26#039;t operate correctly the car won%26#039;t idle properly.|||Others have described what an oxygen sensor does.
Why not take your car to a BMW dealer or independent German car service shop and pay for a diagnosis-only? Or buy a diagnostic code tool and find out what codes are being displayed, then change the part indicated.
I bought a combo oil service and scan code display tool (R5/FCX-II ) from Peake Research for about $150 and it does a good job for both.
