Oxygen Sensor

[tiginbna]

Its finally starting to get a bit warmer here in PA, so off I go to clean, and learn a bit more about my bike. (96 1100GS, purchased in Sept.) As I am cleaning I notice a multi pin screw-in plug on the right side is unconnected, and the female side runs down to the exaust just past the footpeg position. I inquire to my local shop. BMW Moto-Sport in Mechanicsburg PA, (Thanks Jeff), it is an oxygen sensor that has been unplugged. Since I am one of those annoying people who prefer things just so... my questions are...

Is this something to be VERY concerned about?
Is it OK to leave it for a while?
Should I run out and buy a new Ox. Sens. right now?
What are the ramifications of not using one versus using a bad one?
And How can I tell if it is bad?

(Fuel economy has been running in the low 40's over county roads with a few hills, interstates and mountain passes in for good measure, and it has been unplugged since I got the bike)

Thanks

Tig

[tiginbna]

UMMMM..... is there anybody here?,,,, or did I just ask such a dumb question that it does not bear an answer?

It was a serious question.. but as it turns out milage is running in the low 30's not the low 40's as previously reported.

Thanks all

Tig

[manicmechanic]

I've been thinking about that one. The purpose of the O2 sensor is to provide feedback to the computer. If the sensor fails, or is not even there, then there is no feedback, so the 'puter goes to a default mode with a set of instructions for "get you home". So you might be better served to replace the sensor with a new one, as the presently installed sensor is, by now, probably shot. IMHO, the 'puter has gone to "open-loop" mode and is causing you to run rich. What do your plugs look like?

[dano]

I can't tell you exactly what an O2 sensor does, but I can tell you this.

After having purchased my 2003 R1150RT, when I took it in for it's 600 mile service (at 1200 miles) I was told that the 02 sensor was bad. The shop had one in stock and installed it. Within a few minutes of the bike running, it too, went bad. Mind you, these sensors are about $105.00 ea. or so.

So.....they put another one in, and after about 30 minute, it went bad. Well, the shop wasn't going to continue to install them all day long, so they unplugged it from the rest of the system, and told me, that they had called BMWOA tech support, and was told to order in a cat. con. / muffler assembly.

I was told to return in a week, and they'd install the new muffer and another 02 sensor. So, for a week, I was running around with it (o2 sensor) not operating. Prior to me leaving the shop, the lead mechanic even suggested that it would be okay to leave it unplugged permanetly. I asked him if it was your $16,000.00 bike.....what would you do? He replied sheeplishly, I'd have the sensor replaced.

So....bottom line is, my bike went thru four 02 sensors before the problem was cured. But.....who really knows for sure.

I've heard thru the grapevine, that Bosch makes an 02 sensor that fits prefectly, but costs a whole lot less money than does the BMW sensor. Closer to like $25.00 or so.

[alien_hitchhiker]

Tig, this whole set-up makes me suspicious.

I mean, somebody intentionally unplugged the O2 sensor and I'm wondering if they made any other changes. Are you able to talk to the previous owner, and if so, what explanation do they offer?

The sensor was probably disconnected to eliminate surging. Some owners also pull the Cat code plug for the same reason. Is your cat code plug (in the fuse box) present or missing? I think it is pink on a GS, looks like a relay.

Also, is the exhaust system stock?

Both the O2 and Cat code plug tricks work to eliminate surging by enrichening the fuel-air mix, as manic described. Based on your mileage, it sounds like your bike is running very rich. Like manic asked, how do your plugs look? Letting the bike run extremely rich is controversial, not just because of the mileage drop but also becuase it can carbon up the engine and kill the catalytic convertor.

If it was my bike I would (1) reconnect the O2 plug, (2) replace the Cat code plug if it is missing, (3) give the bike a full zoot tune-up (TB synch, plugs, valves) and (4) see how it runs. At that point you will have a bit more to go on.

Keep us posted on how it goes.

Steve-O

[PGlaves]

This is not easy. but I would look for extra wires. It is possible to wire in a variable potentiometer (resister) which fools the Motronic into believing it is receiving a steady reading from the O2 sensor. I'd guess somebody has done this to your bike.