New O2 sensor fixes idle and hot start issue

[Mattlo]

Hello 

 

Wanted to share a successful repair in hopes it might help others with the same issue.

 

This is for a 2000 R1100R with ~22K miles.

 

Symptoms:

• Over the past few seasons the bike exhibited worsening behavior at idle....
• Cold start was fine - caught almost immediately and ran at high idle, with rich exhaust
• Within a minute, idle would drop (even with high cold start lever activated) and I would have to nurse the throttle to keep it running before heading off
• Once under way the bike ran well and hot idle was mostly okay.  
• However on occasion bike would simply die at a stoplight, when at idle.  
• And on occasion engine would die on decel.  In both cases, engine would fire immediately with the starter button
• If hot starting the bike after a few minutes of sitting, it ALWAYS took two jabs of the starter for it to fire.  It never wanted to start on the first cranking, but fired immediately on second.
• Drivable in all cases, albeit annoying

 

Previous fixes:

• As the bike approached 20K, I performed all the usual PM work:
  • Original fuel filter and hoses replaced
  • Valves adjusted
  • New plugs
  • TB synch
  • Scanned ECU for faults (looking for 02 sensor issues);  none were stored
• Results, bike ran slightly better but did not resolve the stalling/idle issue and hot start issue

 

After researching this site and reading comments from Dirtrider and others I considered that perhaps a "lazy" O2 sensor might be the cuplrit (bike had original sensor).  BINGO!!

The bike now runs like it did 20 years ago.  Good transition from cold idle to hot - no need to nurse the throttle.  On  hot restarts, bike fires up immediately first time.

Interesting that even though the sensor had 20K miles (still young??), time had taken its toll.  Sensor itself looked great, no odd colors or buildup on the probe.

 

And shout out to Beemer Boneyard.  They have the OE style O2 sensors in stock.  Fast shipping and great price.

 

Thanks!

 

[JamesW]

Have you ever thought about just removing the cat code plug?  On my early R1100 I had to cut a jumper on the back of the ECU connector which totally fixed the fueling problem and the computer simply no longer looks for an O2 sensor.  I've wondered if this fix would work for later R1100 models.  My bike had a jumper wire instead of an actual removable code plug like I believe your bike has.  I went one step further and tossed the O2 sensor and bought a bung plug at a muffler shop to plug the O2 sensor port.  Bike now runs like it always should have with proper fueling.  No surge and super smooth idle with great fuel economy.

[Mattlo]

Hi

 

Yes, I had removed the cat code plug at some point.  Pink plug on my bike.

However, it ran so rich at idle it made me a bit nauseous.  For me that was a deal breaker.

 

Also, prior to this issue the bike ran fine.  I never really had an issue with surging or otherwise.  

So I was just trying to get it back to the way it was.  Luckily this worked.

[dirtrider]

18 minutes ago, Mattlo said:

Hi

 

Yes, I had removed the cat code plug at some point.  Pink plug on my bike.

However, it ran so rich at idle it made me a bit nauseous.  For me that was a deal breaker.

 

Also, prior to this issue the bike ran fine.  I never really had an issue with surging or otherwise.  

So I was just trying to get it back to the way it was.  Luckily this worked.

Afternoon  Mattlo

 

If it will run to your liking with the o2 sensor working then that is best as they run lean & clean with o2 (closed loop) control. Most 1100's don't therefore the o2 removal. 

 

With o2 removal you do get a richer (and usually higher) idle RPM. 

 

If you decide to ever try the o2 removal again then buy (or fabricate) an Idle Control Valve (Idle Trim Pot) as that allows you to adjust the (no CCP  open loop) idle fueling to be leaner. 

[JamesW]

Hi D.R.,  I really do think mine is an outlier.  Very early on I installed a trim pot but it did not much.  I've been curious what a much newer R1100 would do by just removing the code plug.  On mine after cutting the code plug jumper the bike no longer recognized the O2 sensor and the idle was perfect and smoother than with the code plug jumper installed.  I guess it's just whatever works on these early bikes.  The low back pressure Dominator muffler also smoothed things out a bit more.  I'm pretty much done tinkering.  Do I think I'll be able to tell any difference with the ceramic inside/outside header coating?  Answer:  I'll believe it when I see it in other words I doubt it and I don't see how things can get much better anyway.  

 

Now that I think of it I contacted Bosch by email awhile ago and gave them the model and serial# of the Motronic ECU in my '93 R1100RSL to find out if they would repair if needed in the future and they responded that they had no record of the existence of my Motronic.  That's just great as a new unit would cost just over $2K.  That would pretty much be the end of my BMW riding career maybe, that's a big maybe, I might find a good used one on eBay, maybe.

 

I'm probably going to need another project.

[dirtrider]

2 hours ago, JamesW said:

Hi D.R.,  I really do think mine is an outlier.  Very early on I installed a trim pot but it did not much.  I've been curious what a much newer R1100 would do by just removing the code plug.  On mine after cutting the code plug jumper the bike no longer recognized the O2 sensor and the idle was perfect and smoother than with the code plug jumper installed.  I guess it's just whatever works on these early bikes.  The low back pressure Dominator muffler also smoothed things out a bit more.  I'm pretty much done tinkering.  Do I think I'll be able to tell any difference with the ceramic inside/outside header coating?  Answer:  I'll believe it when I see it in other words I doubt it and I don't see how things can get much better anyway.  

 

I'm probably going to need another project.

Morning James

 

I really  don't know the history of the early 1100RS Motronic control units as those things are a very unique beast. There was really only one closed loop & one open loop map in the early 1100RS Motronic's (that I know of anyhow ).   There was also no CCP socket in the fuse box (they needed a wire cut for open loop operation)

 

The 1100R I am a bit more familiar with & those have some Motronic updates over the years to address some engine stalling issues as the engine went from ride-off cold to short distance warmer. (I have an old service bulletin or two on this somewhere in my pile of 1100 paper form bulletins)   

 

Some of the 1100 engines ran OK with closed loop operation & others were a surging mess at lean-run closed loop, I never tried to track down the Motronic version to see if that was the difference or if it was just a stack up of fueling control issues. Back in the 1100 era most of us just removed the CCP, set the idle RPM down a little then & rode them with a smile. I did play with making some "Idle Trim Pots" for a few to trim the idle richness down a little but the leaner I made the idle the more they surged as that over-rich idle is what carried up into the light throttle surging range to eliminate the surging.   

 

In any case, it looks like the early 1100RS & the later 1100R Motronic's are now all serviced with the same part number replacements.

[JamesW]

Hi D.R., you are correct, there is only one part number for a replacement Motronic ECU and if I needed to replace I would no doubt be in the market for an O2 sensor and hope the closed loop program in the later Motronic revisions will work.  I'm glad the Motronic ECUs seem to be pretty much bullet proof.  At the time my bike was built the same model was sold in countries that did not have emissions standards, hence the great open loop fueling and ignition control but I fear that changed rapidly from '93 onward.  I mean surging was still not uncommon on the later 1150 bikes I know because I had one of them.  Wasn't as bad as my '93 1100 but it was there.

[dirtrider]

7 hours ago, JamesW said:

Hi D.R., you are correct, there is only one part number for a replacement Motronic ECU and if I needed to replace I would no doubt be in the market for an O2 sensor and hope the closed loop program in the later Motronic revisions will work.  I'm glad the Motronic ECUs seem to be pretty much bullet proof.  At the time my bike was built the same model was sold in countries that did not have emissions standards, hence the great open loop fueling and ignition control but I fear that changed rapidly from '93 onward.  I mean surging was still not uncommon on the later 1150 bikes I know because I had one of them.  Wasn't as bad as my '93 1100 but it was there.

Morning James

 

We are starting to go past the OP's information threshold & into the Hijack area as this is getting pretty (early 1100RS specific)  so I will continue via personal message.