Effects of O2 sensor disconnected?
Thread Starter
Instructor
Joined: Nov 2004
Posts: 216
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From: Annandale, Virginia
Effects of O2 sensor disconnected?
I had failed emissions inspection in Virginia three times this month. I replaced plugs and wires, ran a tank of Techron through, etc. All the easy stuff. Each time the readings were worse. 
Today I was diddling with the car trying to figure out next steps when I found the O2 sensor disconnected (behind the fuse panel). Plugged the sucker in, ran the car hard on the highway for 30 minutes to heat it up and adjust the brains, ran over to my inspection station and PASSED by a wide margin. Phew! What a relief.
Now my question. I suspect that the sensor was in the disconnected state for quite some time - at least the year that I have owned the car. How might this have affected my shark? The way it drives, mileage, long term wear, etc?
Any insights welcomed. Now, on to a toast.
Today I was diddling with the car trying to figure out next steps when I found the O2 sensor disconnected (behind the fuse panel). Plugged the sucker in, ran the car hard on the highway for 30 minutes to heat it up and adjust the brains, ran over to my inspection station and PASSED by a wide margin. Phew! What a relief.
Now my question. I suspect that the sensor was in the disconnected state for quite some time - at least the year that I have owned the car. How might this have affected my shark? The way it drives, mileage, long term wear, etc?
Any insights welcomed. Now, on to a toast.
Rennlist Member
Joined: Oct 2003
Posts: 7,210
Likes: 17
From: Nova Scotia
If you now passed emissions, your CAT is working properly: the primary impact of a disconnected O2 sensor is a generally richer fuel mixture. This can be hard on CATs ( not so here 
), and corrosive to the exhaust system. The only carbon steel in a stock system is the main body of the rear muffler ... the rest is stainless.
Likely no noticible impact ... however, you will now have a smaller fuel bill ....
), and corrosive to the exhaust system. The only carbon steel in a stock system is the main body of the rear muffler ... the rest is stainless. Likely no noticible impact ... however, you will now have a smaller fuel bill ....
Thread Starter
Instructor
Joined: Nov 2004
Posts: 216
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From: Annandale, Virginia
Better mileage will be good news. "Hard on cats" - would that make them run hotter than normal? I have noticed quite a bit of heat eminating from underneath the sides of the car.
Thanks, guys!
Thanks, guys!
Rennlist Member
Joined: Feb 2002
Posts: 7,060
Likes: 42
From: Cambridge England
When the LH recognises a disconnected O2 sensor, it just sets the fuelling to a mid range default. This could have resulted in either slightly rich, or more likely lean running.
Regards
Regards
Thread Starter
Instructor
Joined: Nov 2004
Posts: 216
Likes: 0
From: Annandale, Virginia
Sorry for the delay in responding, Meewosh. I couldn't find my emission reports.
I failed three times for HC and CO without my O2 sensor connected. Worst readings:
At 15 miles per hour the HC limit was 55; my reading 212
At 15 miles per hour the CO limit ws .22; my reading 3.16
After attaching the sensor the HC read 6 and the CO .03 - obviously an enormous change. Let me know if you need more data. Good luck.
I failed three times for HC and CO without my O2 sensor connected. Worst readings:
At 15 miles per hour the HC limit was 55; my reading 212
At 15 miles per hour the CO limit ws .22; my reading 3.16
After attaching the sensor the HC read 6 and the CO .03 - obviously an enormous change. Let me know if you need more data. Good luck.
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Thread Starter
Instructor
Joined: Nov 2004
Posts: 216
Likes: 0
From: Annandale, Virginia
I only noticed a smoother idle with the O2 sensor disconnected. My Autothority chip is louder, faster than stock, a tiny bit faster than my Ebay no-name chip and runs rough - especially at hot idle. The Ebay chip also runs faster than stock and much smoother/quieter than the Autothority. Both aftermarket chips' idles are made much worse with the O2 sensor connected and I don't notice any more speed disconnected.
HOWEVER: I have "Thompson grind" cams (GT?) that Rennlisters tell me is responsible for the idle isses. So who knows.
Right now I'm running the no-name chip with the O2 connected and looking forward to taking my baby out now that the ice/snow has melted.
HOWEVER: I have "Thompson grind" cams (GT?) that Rennlisters tell me is responsible for the idle isses. So who knows.
Right now I'm running the no-name chip with the O2 connected and looking forward to taking my baby out now that the ice/snow has melted.
