this is probably a stupid question and it's probably been answered countless times, but i can never find anything searching...so could some please help me? ok my car is running very very rich, and it has been for a while now, otherwise the motor runs very good for the mileage thats on it(136,000)always change the oil on time(mobil 1)and i just replaced everything to do with ignition, cap rotor plugs wires....and set the timing. and it still runs rich, i've never changed the 02 sensor, could this be the problem? when i first got the car, it would start right up, idle at 1800 rpms until it was warm, now i start it the rpms won't hold steady, and sometimes the check engine light comes on, on startup. can anyone help me???? thanks

 

The O2 can cause that kind of problem, I change my O2 once a year.

As they get old they get lazy and do not respond well and the computer then does not really know if the car is rich or lean.

 

Thanks so the 02 sensor could make the car run rich???

 

one more thing, is there any special tools or anything needed to change the 02??? obviously i've never done it before thanks again

 

I just changed mine today. An O2 sensor socket is a must! You can get one at any auto parts store that has tools. It has a slot in the side for the wire.

 

what side would that be on a single cat system?

 

While a bad O2 sensor MAY be the problem, you best check the SES codes first. It may be something else and you'll endup wasting time and money if the O2 sensor is not the problem.

You can jumper the ALDL connector's A and B pins to read the codes. Do a search on "reading SES codes" for more information in the archives.

 

I agree with Glen on this one. Remember, on a cold start the O2 sensor has NO output to the ECM until it reaches about 600 degrees. That is the time it is in open loop and running on predetermined settings in the ECM. If she's running lousy cold chances are you have another problem. ANYTHING that increases oxygen content in the exhaust will push the sensor out of range and trigger an SES. I would start with the basics, vacuum leaks, check TPS setting etc. Also an EGR problem will cause what you are describing. As the moderators always point out there is usually no cut and dry answer without some detective work on your part.

 

Now that i think of it, i did put in a 160 degree thermo a while back...and did not change the chip. and i can't remember if it ran worse after i put in the thermo, if i remember correctly, it just gradually started having the problems i have...and i don't know much about the computer stuff. But i'll definetly look into that...thanks for all your help everyone!

 

My 02 is on the driver side...

 

You are on the right track. If you read some of my other posts about lower op temps you will find that I do not recommend it. I did much experimenting and found that anything but the 195 resulted in lower fuel mileage and a rich condition.

 

well i'm going to try going back to the 195, and change the 02...but in cali i think the car will run really bad that hot. i just want to find out if thats the problem...so i'll try, thanks for your confirmation on that one!