question about o2 sensor
 

Hi everyone. My name is nicki. I have a question about the o2 sensor.. my check engine light is on. I took the vehicle to auto zone and they said it was do to the o2 sensor.. but the o2 sensor was just replace.. I know nothing about cars but I am looking to improve my mph because I am getting very poor gas milage.. the o2 sensor that was replace is the one that is visable from under the motor/engine in the front of the vehicle. Any help would be greatly appreciated.



Thanks nicki

Depending on what year it is ,it could have up to 4.My 96 has 2.1 in the cat and one in the down pipe.

like posted in your welcome post...

there are 2 o2 sensors one on the manifold near the engine, and one after the cat.

The o2 sensor is indeed causing your poor gas mileage and even new o2 sensors can turn bad.

but what is happening is the bad o2 sensor (whichever one it is) is causing the engine to run rich giving you bad fuel economy and at the same time harming your cat...

Is there anyway the sensor could have beeen installed incorrectly? My ex is the one who replaced it. If not then I just need to replace the other one right? Sorry like I said before I know nothing about cars. The jeep has been running really rough lately, almost as if it want to stall out when vehicle is idling. Thanks again..


Nicki

the autozone reader should be able to tell you which one needs replacing, then buy a direct fit/ oem fit to ensure it plugs into the harness and all should be well

If you don't replace the bad O2 sensor soon the running rich condition will ruin the other O2 sensor in no time. It will also ruin the catalytic converter.

^^ I was just about to say that if you hit autozone up again and ask them to read the code... get the code from them as well... but when they look up the code on their computer inside, they can print out a reciept for the exact part you need to fix the issue... as well as they can tell you if it is the up or down stream O2 sensor... I know that my down stream one has to be replaced right now, cause my rear mount for my exhaust is broken and has pulled the wires loose on O2 sensor... no biggie, will fix it once I get the exhaust replaced...

The up stream O2 (closest to motor) is the one that controls air/fuel ratio. The down stream O2 only monitors the cat. Both/either can trigger a CEL. The O2s can go bad or something ahead of the O2s can go bad. Need the diagnostic code(s) number(s).

If your seizes like mine did don't pay the 50+ i was quoted "as long as it came out without problems" (the reason i would take it to a shop anyway) and just buy a new magnaflow cat. I got mine on ebay for $90 bucks on the or best offer thing

It may not be the O2 sensor just because there is a code for the O2 sensor. A vacuum leak can cause an O2 sensor code to flash, low fuel pressure can do it too. There is more to dianostics than reading a code and replacing a part. You have to varify the part you are about to replace is the problem BEFORE you replace it.

Exactly...Mine was spitting and sputtering at idle and had a check engine light that was pointing to a bad o2 sensor....After checking the fuel pressure I found out it was a bad fuel pump. The pressure would start out at 47psi and after a few minutes it would drop down to about 20psi and start running rough and then it would go back up to about 47psi and start running smoothly. After replacing the fuel pump everything is good...................

...........but you need any and all codes 1st, that will eliminate or greatly reduce the amount of guess work and u go from there.

True, but I look at them more as clues than codes. They will help clue you in to what the problem is, not pinpoint the problem. Lets say your CEL comes on, you go to Autozone and have the "parts guy" plug into the diagnostic connector and pulls up a code for "MAP sensor voltage low". You just going to walk into the store and buy a MAP sensor? No, you're going to atleast look and see if it is even plugged in first. That code gave you a clue on where to start looking. Those code readers really help the parts stores make money. Code are a little help, but the data stream is even more helpful. It is nice to see what is going on real time.

Ahhhhhh......that's why I finished my post with "and u go from there". Dealer service dept, independent garage, parts store tech.....doesn't make much difference, 1st thing any/all of them will do is plug in and scan for codes and go from there.

And I'm saying just because there is a code does not mean that the component that the code points out is bad.