Motronic codes -O2 sensor??

Hello Oilhead community,

Bike: 1994 R1100RS. 49,337 miles.

I’m still trying to take care of an intermittent rough idle/intermittent surge condition. Symptoms:

1. Intermittent rough idle (only happens occasionally once engine is fully warmed up. When idling ‘rough’ feels like there’s a stumble or kind of a misfire (not like lack of ignition but lack of enough fuel)

2. Intermittent surge. Mostly runs smooth, but occasionally surges. Does this in conjunction with rough idle.

3. Pinging at heavy throttle applications, once again intermittent and only very occasional. May be seldom since the weather has cooled off quite a bit.

I pulled codes from the Motronic, I pulled:

1215 butterfly valve sensor (tps)
1111 CO potentiometer

I pulled #5 fuse for a couple of minutes then re-checked the codes. 1215 is gone but 1111 remains. Weird!

Valves clearances are in spec. Spark plugs are new-ish. Fuel filter is fairly new. Internal and external lines were replaced a few years ago. TPS has been set, TB’s are tight and are synced. I’ve been really working on this one, I LOVE riding this bike and badly want to get this issue worked out.

I feel like it could be the 02 sensor, it makes sense since this problem is intermittent and comes/goes.

Any ideas or suggestions?

Denny

The 1111 code could be a ghost, or not. I had that code in my bike but RealOem showed I should have the CO potentiometer. I bought one, by Bosch part number, not BMW part number, dropped it in and immediately saw cold start/idle improve. Improved so much that literally, 200' down my driveway, halfway to my first stop sign, another 200', I was off the cheater lever.

Still though, a good tune-up is always the place to start and newish plugs could be like the pair I just bought for my tractor. One was good, the other was bad. Bought two more, success rate is 75%.

Have you ever had the fuel injectors removed and cleaned professionally? A pro injector cleaning service will clean, replace filters and o-rings and provide a report to show how closely matched they got the flow rate. Not expensive.

dennyd said:

Hello Oilhead community,

Bike: 1994 R1100RS. 49,337 miles.

I’m still trying to take care of an intermittent rough idle/intermittent surge condition. Symptoms:

1. Intermittent rough idle (only happens occasionally once engine is fully warmed up. When idling ‘rough’ feels like there’s a stumble or kind of a misfire (not like lack of ignition but lack of enough fuel)

2. Intermittent surge. Mostly runs smooth, but occasionally surges. Does this in conjunction with rough idle.

3. Pinging at heavy throttle applications, once again intermittent and only very occasional. May be seldom since the weather has cooled off quite a bit.

I pulled codes from the Motronic, I pulled:

1215 butterfly valve sensor (tps)
1111 CO potentiometer

I pulled #5 fuse for a couple of minutes then re-checked the codes. 1215 is gone but 1111 remains. Weird!

Valves clearances are in spec. Spark plugs are new-ish. Fuel filter is fairly new. Internal and external lines were replaced a few years ago. TPS has been set, TB’s are tight and are synced. I’ve been really working on this one, I LOVE riding this bike and badly want to get this issue worked out.

I feel like it could be the 02 sensor, it makes sense since this problem is intermittent and comes/goes.

Any ideas or suggestions?

Denny

Click to expand...

Denny,
The TPS code most likely occurred if you adjusted the tps during the TB Sync. Now that you’ve cleared it by disconnecting the battery it shouldn’t come back.

The CO Pot error means that your Motronic believes that your bike doesn’t have an O2 sensor and that there iis no CO Pot installed. The Motronic learns whether it should use the O2 sensor from: either a Pink or Yellow coding plug in the electrical box; or, in early 1994 bikes from the same coding plug function achieved by grounding pins wired in the electrical harness. So if there is no coding plug or someone cut the pins in the electrical harness, then the Motronic thinks it should have a COPot. In R1100 bikes (other than the S), it was common for riders to try and fix surging by pulling the plug or cutting the wires.

Usually these R1100 bikes idle fine with the coding plugs removed and no COPot. But the COPot is used to lean out the mixture at idle and light throttle. Without the coding function and a working O2 sensor (yours may be old or disconnected under the tank), and no COPot, some of these bikes are too rich at idle, especially so if R1200 injectors have been installed.

The next step is for you to try and figure out how the above applies to your bike, meaning does/did it have a plug and/or an O2 sensor and is that connected.

You could also shotgun this and buy a COPot and try adjusting it for a better hot idle. That may or may not working, depending on the above. If your bike is still coded for an O2 sensor, and one is installed and working, a COPot doesn’t have effect. Maybe you could borrow the pot from someone who doesn’t ride in the winter.

Usually a COPot is adjusted until exhaust carbon monoxide hits a certain figure, but you can just twiddle it until the idle is best as an alternative.

And none of this may apply, the 1111 error could be due to the above but your idle problem may be something else, like injectors.

Thanks everyone for your insightful advice. I my VIN on realoem and it does have an 02 sensor with no CO Pot.

Next steps for me are to trace the wiring from the bike to the 02 sensor and make sure the wiring is good and see if I don’t happen to have a bad 02 sensor, or it’s unplugged, or bad wiring/connection. Finally, as a winter project I’ll take the injectors out and have a local FI shop check them out and service them. It seems to be a cheap enough service to do.

Thanks again!

Denny

‘04 R1100S, ‘94 R1100RS

In addition to tracing the O2 wiring you need to see if there is a spot for a coding plug and/or fixed wiring in the harness. The O2 won’t work without one or the other.

Thanks Roger. I should have mentioned I do have the yellow coding plug.

Tonight I unplugged my o2 sensor while the bike was running, with the result being a non-intermittent rough idle with rough, surging partial throttle, similar but perhaps a little worse than when my condition is present. Plug the sensor back in, and within 10 seconds or so the bike is back running smoothly.

At this point I think my best bet is to replace my o2 sensor and have my fuel injectors professionally cleaned and go from there.

Denny