Rough Idle - BMW R1200GS Forum : R1200 GS Forums
 
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post #1 of 9 (permalink) Old 12-Aug-2009, 08:18 PM (054) Thread Starter
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Rough Idle

While riding today I noticed that while sitting at stops the engine was idling rough - almost like it wanted to stall but instead of seeing if that would happen I eased the throttle on a little to raise the revs.

2008 R1200GS - about 4900 miles

Any thoughts - could be the cruddy California gas I guess - always use the premium tho...

Thanks!
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post #2 of 9 (permalink) Old 12-Aug-2009, 09:07 PM (088)
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Your bike is still new, as in parts are still changing/breaking in, new. You are about 1000 miles away from your next service/valve adjustment and 4300 miles since your last adjustment. A little roughness is to be expected. It should go away after your next service.

The roughness between services should get less over time as the bike breaks in.
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post #3 of 9 (permalink) Old 12-Aug-2009, 09:50 PM (118) Thread Starter
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Talking

Yeah, but prior to today it's been fine... kinda paranoid since I had the fuel pump replaced about 6 months ago maybe it's because I scheduled the annual mx this morning... ( Motorcycle phycology)
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post #4 of 9 (permalink) Old 30-Oct-2010, 11:41 AM (695)
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Rough Idle

I have a 2005 with 13K miles. So far I've replaced the spark plugs, set the valves, synchronized the throttle biddies and calibrated the idle stepper motors. I verified the throttle cable is not holding ether butterfly open. After doing all these things it still consistently idles rough. It seems like it's fighting itself almost like it's firing to soon, but runs great off idle. Temperature seems to make no difference. Any ideas?
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post #5 of 9 (permalink) Old 30-Oct-2010, 09:44 PM (114)
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Don't idle the bike?

Apparently the steppers that control idle on both sides can get out of sync. The dealer can use the GT1 to sync the steppers or someone with a GS-911 can do the same. That isn't a guaranteed "fix" as there may be no problem to fix. BMW specifies an allowed side-to-side mismatch at idle of up to 25 mbar with the steppers parked. The GS-911 can park the steppers for that measurement, too.

If the mismatch is greater than 25 mbar the issues is usually one of an air leak or a bad valve adjustment. Check for air leaks. A bad charcoal canister solenoid or line from the solenoid to the left throttle body counts as an air leak.

And while were talking about the charcoal canister... is it always rough at idle or just once in a while. The bike purges the charcoal canister once in a while and I'd expect it to roughen up a bit when that happens.

Last edited by marc; 31-Oct-2010 at 01:45 PM (781).
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post #6 of 9 (permalink) Old 31-Oct-2010, 07:26 AM (518)
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Awhile back a forum member showed what I thought was pretty good
smarts in trouble shooting your type of problem. On close inspection he
found that the throttle body on one side had not been (re)installed
improperly into the intake manifold (black rubber/plastic) and was
allowing air to leak (vacuum) more into one throttle body than the
other...thereby leaning one cylinder over the other. There are
O-ring seals which indicate how critical this connection is
considered by BMW.

The upstream seals between the air cleaner and TB may not be
as critical as it appears that BMW does not use any air mass
sensor in the TB. Contra, the intake manifold is seeing
air and fuel and excess air on one side would unbalance
the air/fuel mixture causing rough running. There might be compensation
for this in the knock sensor-ECU(BMS-K) system but who knows?
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post #7 of 9 (permalink) Old 01-Nov-2010, 08:14 AM (552)
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All good points. I have verified there are no vacuum leaks and have used the GS-911 to calibrate the steppers. A few more data points to add. I did a castrerectomy capping the vacuum port at the throttle body. Also the throttle is very on/offy. From idle I can't smoothly increase the rpm or even hold it at 2K rpm. It's ether increasing or decreasing. The bike did sit for a year. I drained the gas and have put about 600 miles on sense, with no change to the idle.
Thanks for the help.
Brent
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post #8 of 9 (permalink) Old 01-Nov-2010, 01:51 PM (785)
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Quote:
Originally Posted by stuckinmud View Post
Also the throttle is very on/offy. From idle I can't smoothly increase the rpm or even hold it at 2K rpm. It's ether increasing or decreasing.
Fuel injection. You've described what some folks call fuel injection snatch or throttle snatch and is the nature of the beast. Some bikes have it worse than others. Add on's like the booster plug or the accelerator help some folks, but the issue never goes away. For some bikes (not the R12GS) there is an after market in throttle cams to minimize the problem.

One thing you can try is to hook up your GS-911 and monitor the real time values of the O2 sensors. Sometimes you will see one sensor bouncing all over its range, exacerbating the issue. There was a recent posting regarding this kind of troubleshooting on the MOA forum.
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post #9 of 9 (permalink) Old 01-Nov-2010, 05:11 PM (924)
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Marc is right to look hard at your oxygen sensor.

If you ask Mr. Google about oxygen sensors you will see that
the internet vibrates with info and experiences that
profile your issues..cars and motorcycles ...all brands...with
the general feeling that it is the Oxygen sensor that effects
the drivability issue across the modern computer controlled
combustion engine fleet.

Here is an older article that seemed pretty heads up: http://www.wellsve.com/sft503/counterp_v2_i3_1998.pdf

Off the GS-911 board..guy fighting same thing on RT: http://groups.google.com/group/gs-91...cd4bb82239f74#
A couple of the guys are pointing there finger at both
the Oxygen sensor and the Hall effect sensor or at
least the wiring to the Hall effect sensor.

Last edited by pdxrmccgs; 02-Nov-2010 at 09:18 AM (596).
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