running off-road exhaust...do i still need both sets of O2 sensors???

[bigsterl97]

i have a 97 cobra and i am running without cats...i have had issues in the past passing emissions so i bought a pair of O2 sensors and the MIL eliminators from american muscle. i know the car has 4 O2 sensors but i was told the the pre-cat sensors don't do much of anything. i am set to change out the post-cat O2 sensors and add the MIL eliminators so i was wondering if i should just go ahead and switch out all 4 sensors or just the post-cat ones...any suggestions?? :shrug:

 

[VirtualSVT]

First 2 yes. Last 2 no.

 

[STAMPEDE3]

Someone told you backwards.

The front (Pre-cat as you called them) do your A/F adjustments.

The rears (After cats) are not needed but will need mils or to be turned off in a tune to avoid the CEL.
Keep in mind that even with Mils the sensors need to be good unless they are turned off.

 

[bigsterl97]

thanx guys...i will go ahead and buy another pair.

 

[USMC53CHIEF]

i have mils elims on mine and my light still came on for a circuit fault.. going away with a near future tune

 

[97cobra...]

i just took my cats out and turned of my rear o2's with my sct tuner but today my cel came on and said system too lean bank 1 those are the front right? sorry for the thred jack

 

[JasonSnake]

I'd say drive it for a little while and allow the PCM to adjust to the new a/r. If the CEL is still on after about 50+ miles, then definitely worry.

 

[workmangc]

thanx guys...i will go ahead and buy another pair.

Why do you need another set, Do you not have any in there at all? If you have some in there, just get the MIL-eliminators. If you have a tuner, just turn off the rear O2's.

I'd say drive it for a little while and allow the PCM to adjust to the new a/r. If the CEL is still on after about 50+ miles, then definitely worry.

I don't believe is good advice. The computer has already tried to compensate for a lean condition, but is unable to. If it was within tolerance then he wouldn't have gotten the code.

I would suggest that he look for another cause, perhaps he will be lucky and it will be a vacuum leak.

 

[bigsterl97]

i have a SCT handheld tuner...i didn't know i could turn off those O2 sensors with that...that is why i thought i needed to get a second pair of sensors. will it prompt me to that or do i need to know how to get to it?? can i even do it at all with the handheld SCT tuner or do i need to get a professional tune for them to be turned off??

 

[bigsterl97]

i just took my cats out and turned of my rear o2's with my sct tuner but today my cel came on and said system too lean bank 1 those are the front right? sorry for the thred jack

its cool...i am feeling those rims and how good the paint it on you PG. i need to get a better pic in my sig of the cobra