: O2 Sensor



94CaddyConcours
09-19-05, 04:37 PM
HOW MANY O2 SENSOR DOES MY NORTHSTAR HAVE AND WHERE ARE THE LOCATION.
MY CAR RUN NORMAL EXCEPT THAT IT GET ONLY 12 MPG. SO I THOUGHT THAT IT COULD POSSIBLY BE THE O2 SENSORE SINCE I CHANGED THE SPARK PLUG. ALSO LONG BEFORE THIS I HAD A BAD COIL PACK AND UNBURN FUEL WENT TO MY EXHAUST AND CAUSE IT TO BE FLAME RED. IS THERE ANY WAY I CAN TEST IT. IF IT IS NOT THAT THEN PERHAP I SHOULD JUMP TO CHECKING THE INJECTOR(CHECK IT LAST=MORE EXPENSIVE) ANY ADVICE WOULD BE THANKFUL
BILL SONG



http://i11.photobucket.com/albums/a183/THAMAUP/WILLCAR.jpg

mcowden
09-19-05, 05:11 PM
You already posted this elsewhere on the board, and I answered it there. Not sure why you needed to post it again, but regardless, here is the answer.

There are 4 oxygen sensors. One in the front exhaust manifold, one in the rear exhaust manifold, one just in front of the catalytic converter, and one behind it. The two before and after the catalytic converter use one model sensor, and the other two use a different model. They are all heated oxygen sensors. Failure of any of them can result in reduced power and gas mileage and other negative symptoms that depend on the condition of lots of other factors. When they get crudded up or just go bad, only the bad sensor needs to be cleaned or replaced. You do not need to replace all 4 sensors when one stops working properly.

Replacement sensors vary in price from about $50 to about $75 each and it is generally best to stick with "OEM-style" sensors rather than Universal ones because the Universals require you to splice the wire harness, and that's just asking for trouble. Removal and replacement can be done with a few basic tools that include a special oxygen sensor socket or 7/8" crow's foot socket and possibly a long 3/8" extension, depending on the model and year of car.

When one or more of the sensors is not performing adequately, you will probably see a "SERVICE EMISSIONS SYSTEM" message on the dash and the Service Engine Soon light will illuminate. If you search the forums, you will find many good descriptions of the procedure to read the diagnostic codes. The codes will tell you exactly which sensor is misbehaving and what it's doing wrong. If your car has any DTC codes stored, look them up at the following web site for '96 or newer cars:

http://myweb.accessus.net/~090/dtcobd2.html

Or at this site for '95 or older cars:

http://myweb.accessus.net/~090/dtcobd1.html

Let us know if you need any help. Good luck.