Downstream Oxygen Sensor?

[ezysk]

As some may recall I am currently in the process of giving my newly acquired 94 Firebird with the powerful 3.4L a tune up.
The parts store lists an upstream oxygen sensor and a down stream sensor.
I am assuming the down stream is the one after the catalytic converter.
I picked them both up and then when I got under the car I found that there appear to be 2 oxygen sensors right near the engine on the exhaust pipes, one on each side of the engine. I also discovered that someone appears to have removed the CAT. and replaced with a straight pipe. I also noticed there is no downstream oxygen sensor.
Who ever did it did a good job because I cannot find a single cut wire, or cut tube or anything.
I also did not have any engine codes or anything when I drove the car, so I began to wonder the following.
1) Did all 94 Firebirds have Catalytic converters on them?
2) Is there a downstream oxygen sensor?
3) Shouldn’t there be a check engine light or something if there was supposed to be a downstream sensor and it was removed?
4) If it was supposed to be there and is removed, what would this, or should this cause any problems?
Thanks,

[Bad_Z28]

I'll do my best to help on this.......

1994 Firebirds should have had a downsteam O2, however I believe it's simply for "monitoring" purposes and doesn't actually play a role in ignition, timing, or air fuel ratio. And on OBD1 cars the O2 can be un-plugged without throwing a code. With the downstream O2 removed you should have absolutely no problems. Good luck with the tune up!

[BP_Z28]

tuneups on 3.4s kick ass

[1BADAIR]

obd1 shouldn't have post cat o2's

[BP_Z28]

obd1 shouldn't have post cat o2's

we just have 2 single wire 02s before cat wooooooot

[meissen]

obd1 shouldn't have post cat o2's

Yeah, I was going to say I replaced my O2's and I only had the two upstream, not downstream.

I also believe all vehicles -- at the very least, since the mid 80's -- had catalytic converters. I know the 4th gens all did, at the least.