O2 Sensor - damage to Catalytic ?

[jcsjcs]

Hello - I just discovered my newly purchased 84 911 had an unplugged O2 sensor. I am replacing the sensor tomorrow, but am curious about possible damage to my catalytic converter. Anyway to test this?

[ttweed]

I don't think a non-functioning O2 sensor is going to damage your cat, but I know little about the later cars and their emission systems. Where are you located? Do you need to meet smog regs or something? If not, I would just gut it, or install a straight flow test pipe. If you do, go to a smog station and ask for a "pretest" run and check your emission levels. If you have low emission levels, then the cat is probably working OK.

TT

[jcsjcs]

I just purchased the car and somehow they did not pick up the disconnected sensor on the PPI. I recently read in 101 Projects for the 911 that running rich can damage the cat - so I am trying to guage the damage to my wallet from this issue.... so I can decide if I want to pursue with the seller and PPI mechanic.

Definitely need to replace the O2 sensor - and then will check out the cat afterwards - I like your suggestion to get a pre-test run.

I am not 100% comfortable bypassing the Cat - as I will have inspections issues down the road (and have some Green guilt...) but it is worth considering.

[JohnKo]

The O2 sensor is part of the 'feedback' system that senses oxygen content in the exhaust and acts as an input for mixture control. Its main purpose is to keep the air:fuel mixture in a range that allows the cat to clean up exhaust emissions. Increased efficiency is a bonus. Running too rich or too lean are both bad for emissions, but it's running too rich that can cause the cat to overheat and get plugged up. If the car runs okay the way it is (i.e. no excessive exhaust restriction), the cat is probably okay. The disconnected O2 sensor might be masking some other problem, or maybe the PO just didn't want to bother replacing it. Go ahead and replace it.
john

[Zeke]

Search here for the Ford O2 sensor replacement at half the cost. I have one and it works perfectly (well, it passed smog whereas the PO couldn't get it passed).

[hcoles]

I found that my car ran ok with sensor unplugged..therefore probably no damage to cat. You may check other threads re. replacing the sensor with a generic and soldering in the wires to save a few bucks. You can run with test pipe and put cat in on smog test day... the test pipe should have a sensor bung. This saves the cat and you can loan to friends who have bad cats on thier smog day. I notice that the engine seems to run much cooler with cat out. Not sure but these cars may pass smog with the cat out if all is in great condition... but not the visual part of the test if the guy knows what he is looking at.

[jcsjcs]

Last night a friend and I removed the old O2 sensor - which was a generic BOSCH that was soldered to the standard leads. It was rusted in AND cross threaded - total pain to get out. Then getting in the new BOSCH sensor made for my car was a challenge due to the cross threading. Finally got it hooked up - a 30 minute project that took 1hr and 30 minutes and all is well. I am running with an O2 sensor again and the car seems a bit smoother under full throttle though idling is a little rough.

Not going to bypass the CAT for now - though I will keep it as an option for later on... Already started looking at exhaust upgrades - but that is probably a year or so down the road.

Thanks for all of the input.