will misconnected o2 sensors lead to cat failure?

[DrScientist]

1991 850i

a few posts down, i noted my cats have failed: rattley shakes when going over bumps for about 300 miles (i thought it was the body work of the side sill), followed by misfires while driving, now no power with throttle after warmup, steady idle.

anyway, after reading a few posts on the o2 sensors and their crossed connections, i realized my shop had the entire exhaust off when doing some suspension work a few months back. (they're a good crew, but not sure everyone there has expert m70 knowledge) i tried to take a look up there, but my eyeballs couldn't tell if they actually were connected appropriately... not that i even know what to look for.

car had ~107k miles going into the suspension work. now has ~108k. is it possible they misconnected the o2 sensors? and that has lead to the cat failure? would 1000 miles be enough to cause this? or is it more likely the originals are just old?

[dragon850]

1991 850i

a few posts down, i noted my cats have failed: rattley shakes when going over bumps for about 300 miles (i thought it was the body work of the side sill), followed by misfires while driving, now no power with throttle after warmup, steady idle.

anyway, after reading a few posts on the o2 sensors and their crossed connections, i realized my shop had the entire exhaust off when doing some suspension work a few months back. (they're a good crew, but not sure everyone there has expert m70 knowledge) i tried to take a look up there, but my eyeballs couldn't tell if they actually were connected appropriately... not that i even know what to look for.

car had ~107k miles going into the suspension work. now has ~108k. is it possible they misconnected the o2 sensors? and that has lead to the cat failure? would 1000 miles be enough to cause this? or is it more likely the originals are just old?

Well yes theoretically this could kill your cats since it will run very rich. Do you have check engine light on? EML light on?
Fyi Walker cats are superior to Magnaflow.
Are you sure you are running on 12cyl?

[liquidblueloft]

Anybody have a picture or diagram of the correct hookup for the o2 sensors. That would probably help him out best. I see to remember one on here somewhere before but I can't seem to find it in the search. I could probably take one of my on Friday when I get my cats removed.

[masbury]

I don't know if it will kill your cats, but if the O2 sensor wires are crossed, you will get a max lean on one bank and a max rich on the other as they try to compensate. No cel, just codes.
Have your codes checked. If you have above, reverse the cables and re-read the codes after clearing. Should be okay.

[dragon850]

I don't know if it will kill your cats, but if the O2 sensor wires are crossed, you will get a max lean on one bank and a max rich on the other as they try to compensate. No cel, just codes.
Have your codes checked. If you have above, reverse the cables and re-read the codes after clearing. Should be okay.

I have heard other say they got no CEL but I have tried switching my o2 sensors on purpose and definitely got a CEL plus car ran very crappy.

[DrScientist]

car is a pre-obd-ii. i didn't even bother to find a port to connect to, let alone have anything to connect to it!

no check engine lights.

it does appear i'm running on all 12 (or at least some from each bank) when i put my hand in front of the exhaust tips from either side.
drivers side exhaust tips very sooty, passengers not so much. only passenger's exhaust tips show any condensation coming out at first start.

dragon, when you swapped your o2 sensors, was the change noticeable immediately? i've been driving the car for a solid 1000 miles with a gradual built up to what i have now. so maybe these things were just on their way out.

anyway, going to have the new ones welded in today.

thanks guys

(where are those guys who are always saying they want to buy old cats?)