kevinpaul

Hello everyone, I am the proud new owner of a 98 mustang gt. When i bought it he told me the check engine lieght was on because of the o2 sensors. He showed me two plugs and said they needed to be plugged in to get rid of the light. They didn't seem to work for him so he removed them.

I was going to put them back on this morning, but when I got under the car I realized there were 4 O2 sensors, not two. So I do not know which two sensors to plug into...

I also read somewhere on the internet this morning that those are not always the best option. It then mentioned reprogramming the computer for the h-pipe or replacing the chip with one that was pre-programmed for the h-pipe would be the best way.

I do apologize if this is common knowledge, with so many options and manufacturers out there, and my speedy 28 k modem, Its hard to find the answers I need. Thanks..

I most concerned with which one is going to give me the best performance. Secondly, the cost. If reprogramming and installing a new chip achieve the same results, which one is cheaper.

ChalknCover

There are 4 o2 sensors as you stated. The first two are pre-cat (they are before the cat convertor) the second pair is post-cat (you guessed it, they are after the cats). The first pair is the most important as it effects the a/f ratio of the car, the second pair can be tuned out. With tuning, you program it that the rear o2 sensors are not present. It really doesn't matter either way. Another option is to get MIL eliminators to plug into the rear 02 harness.