why disconnect the O2 sensor?

[dvkk]

Why does everyone here disconnect their O2 sensor? Is there a perception of more hp? My understanding of FI is that they all go to a rich condition at WOT, so that can't be it.
Is it that you are all trying to pollute more? You enjoy failing your state smog inspection?

[CarreraS2]

Do everyone really disconnect their O2 sensors here? I've never noticed that.

On a CIS car, I suppose it would give one more control over the mixture. You wouldn't have the Lambda box constantly correcting it.

On a Motronic car, I don't think there would be much advantage. It seems that if disconnected, it defaults to a rich position, which probably isn't optimal. On the BMW list, a lot of guys with the older Motronic cars seem to disconnect 02 sensors as a "Band Aid" to get their cars to run better. Like the car has vacuum leaks or other problems, and disconnecting the O2 makes it run a lot richer, which smoothes out the idle and "fixes" other running problems.

[Superman]

My CIS system will make the mixture REALLY LEAN at idle, if you let it. Unplugging the O2 sensor prevents this. I believe that this does not affect the mixture at other engine speeds, WOT, etc. It's just a really really lean condition at idle. Like .8% versus 3.5%. Since disconnecting he O2 sensor, my spark plugs are not nearly as white.

[UTKarmann_Ghia]

Mine was disconnected when I bought the car. Being the ambitious guy I am, I decided to put in a new one and hook it up. I even had the mixture adjusted by the local Porsche wrench, but it made my car run VERY VERY HOT (once to 270). When I finally figured it out, I yanked that sucker never to be seen or heard from again.

sue me...

[dvkk]

Originally posted by Superman
My CIS system will make the mixture REALLY LEAN at idle, if you let it. Unplugging the O2 sensor prevents this. I believe that this does not affect the mixture at other engine speeds, WOT, etc. It's just a really really lean condition at idle. Like .8% versus 3.5%. Since disconnecting he O2 sensor, my spark plugs are not nearly as white.

I wouldn't call .8% "really lean". Why do you care what the mixture is when your foot is off the throttle?

[Vipergrün]

dvkk, most of us who have removed/disconnected the O2 sensor have done so in conjuntion with other changes. These include setting timing to more advance and purposefully richening the mixture. The O2 sensor will try to keep the mixture lean. BTW, I just passed CA smog without an O2 sensor OR a cat (mine was gutted). As far as pollution, if you want to go on the attack, try the H2, Excursion, Suburban boards.....

[VaSteve]

Since I'm still waiting on some books and such, can one of you supply a photo of where the O2 sensor is, so I can check on it?
Thanks
Steve

[Vipergrün]

Originally posted by VaSteve
Since I'm still waiting on some books and such, can one of you supply a photo of where the O2 sensor is, so I can check on it?
Thanks
Steve

Steve, take a peek behind the rear driver side wheel. You should see the O2 sensor in the catalytic converter. It *should* have a wire coming from it which goes into the engine compartment.

-B

[Tim Walsh]

Steve,
I had this exhaust system on my T when I first bought it. Here's a pic.

[Superman]

My mixture is perfect. The dyno guy was the most recent to make this observation. It is more than FOUR TIMES the richness of emission spec (0.8%). I'd say that's lean. Emissions regulations in 1983 required that this super-lean mixture be achieved at idle. So, this spec was designed to please not engineers or mechanics or engines or owners, but emissions technicians. I don't meet any emissions technicians, so without the opportunity to impress them, I'm just going with what is most pleasing to engines, engineers, etc.

Perhaps my CIS system would lean this mixture during steady-throttle cruising. In that case, there'd be detonation from the moment I mashed the throttle until the moment the switch told the computer that I intend to accelerate. That's just wrong. Emissions spec is not the "right" mixture. These engines get away with it for the most part, but it is the "wrong" mixture for engine health.

besides, I like the smell. Rich mixture smell beats rotten eggs every time.

[VaSteve]

Tim,
The orange thingy to the right of the red shock?
You come through again, man!
Steve

[VaSteve]

Of course, I just went out and checked and it appeared to be plugged in. I could only test by feeling, since there's a shield in the way.

Back to the drawing board.

[stlrj]

Most often the 02 sensor is disconnected out of ignorance and the lack of skill to set up the injection system to make it work the way that it was designed.

So the fast and stupid solution is to disconnect it.

Cheers,

Joe Garcia
86 Carrera
Redwood PCA since 1976 ( former tech chair)
Building systems engineer
Automotive Computer Controls Technician

[Tim Walsh]

steve,
yes that orange thing is the shock. It's a koni. There's a little bung to the right that's the o2 sensor.

[chuckr]

Most often the 02 sensor is disconnected out of ignorance and the lack of skill to set up the injection system to make it work the way that it was designed.

So the fast and stupid solution is to disconnect it.

.... with statements like this, no wonder your are FORMER tech chair

[VaSteve]

No, no. I meant this thing in the circle. (It's kinda orange too...)

[stlrj]

Sorry if you are offended by this, but it was not intended to offend anyone as I would be the first to admit my ignorance and stupidity on more than I would like to admit.

Having been on both sides of the fence, I can recognize ignorance when I seez it.

Joe

[KFC911]

Steve, on my 3.2, the O2 sensor looks quite a bit different that the one on Tim's car (and I'm guessing that your SC is probably more similar to mine). Although it isn't a 'clear' shot of the O2 sensor, the following pic shows mine (approx. 2 1/2" tall). I've also got a euro premuffler which replace the cat.

[jester911]

That is a pic of the sensor, but Steve you need to look in the engine bay to see if it is plugged in.

Look on the left side down at the bottom of the bay the wire comes through the metal next to the wheel well it has a connector
that may or may not be plugged in.

[KFC911]

Here's a smaller resolution (and I'm practicing posting pics !):





edited...why do my pics appear as a link instead of the actual pic?