o2 sensor question. confused.. help!!

[pacefarm]

i got a '97 240. replaced the stock downpipe on the ka, and the exhaust with 3" piping in preparation for the turbo. i know there was a cat in the stock downpipe, so that's now out. i welded on an o2 sensor bung on the 3" downpipe for the sensor. well, i guess one night all the vibration from the engine caused the o2 sensor to rattle loose and fall out. check engine light came on, car started idling rough too. the sensor got pretty beat up as well, since it was hitting the ground when that happened. i put the sensor back in, since supposidly it doesnt do much but monitor the cat condition. but if it doenst do anything but throw the check engine light on, why would my car start idling rough and have a hard time starting?? any ideas? would getting a o2 sensor simulator help the problem, since o2 sensors are so damn expensive... thanks in advance.

[projectRDM]

Which one fell out?

The first one is the primary, you need it for proper A/Fs, otherwise it runs open loop. If it hit the ground it's trashed, replace it. The secondary sensor below the car serves for OBD purpose only to verify catalytic converter operation, you don't need it at all.

[pacefarm]

thats why i'm lost. its the second one, and the car started acting up after it got beat up..

[projectRDM]

Well, if it's damaged that could throw another code altogether. Unplug it. And make sure you plug up the hole in the pipe or where ever it was mounted. Also double check fuses, the damage may have blown the fuse, it also runs the front O2 sensor and the TPS.

[pacefarm]

Well, if it's damaged that could throw another code altogether. Unplug it. And make sure you plug up the hole in the pipe or where ever it was mounted. Also double check fuses, the damage may have blown the fuse, it also runs the front O2 sensor and the TPS.

TPS? sorry, a bit of a newb...

[projectRDM]

Throttle position sesnor, but I made that post too quick, that fuse doesn't run the TPS, only the O2s.