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Old 06-02-2015, 09:11 AM   #1
paulh24adv OP
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Joined: Mar 2014
Oddometer: 7
BMW 650 stalling, what next?

Hi, I have an '09 Xcountry and it's driving me nuts!!!

In short...

'Developed the cutting out habit at around 12k miles. 'Tried following advice on this forum and others.

Started with the simple non-invasive items, then a few others...
TPS resets, battery voltage, O2 sensor connector, injection cleaner, cleaned airbox interior, injector, idle actuator, 'joined' the battery leads, changed to iridium plugs (see Note below), but she's still misbehaving!

Very often she seems OK 'ish after some TLC but after a couple of short trips she's at it again!

Note: When changing the plugs I discovered that the wiring to the coils was reversed, swapping them over has resulted in a noticeable improvement in performance in Open Loop conditions (I'd advise everybody to check this), but not Closed Loop, especially at idle which often seems weak.

Next I'm going to try running only in Open Loop (by disconnecting the O2 sensor) to confirm that the issue is related to Closed Loop running only, then what? Any ideas?

Will any GS911 owner help me out with a fault code check please, I'm in the UK near Peterborough?

Cheers, Paul
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Old 06-02-2015, 09:44 AM   #2
The Jester
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Location: Cornwall, UK
Oddometer: 866
I would definitely try it with the O2 sensor disconnected. This will do no harm to the bike. I am wondering whether your sensor has developed a fault. They do have a finite life and it could be that yours needs replacing.

On a slightly different tack, when I had my Xch I ran it for a while with an injector that flowed 10% more than stock. Once the O2 sensor was removed the bike ran really well, far better than stock. Of course the downside to this is it also used about 10% more fuel, but this was partly down to me making use of the extra power. If you do a search of the Xch threads you will find the part number
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Old 06-23-2015, 06:57 AM   #3
paulh24adv OP
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Thanks for the info' Jester, I haven't even tried the O2 disconnect yet because 'as if by magic' the problem has almost gone away without further action!

I've covered another 300miles of mixed riding including two 50mile trips and a lot of shorter stuff in traffic and although it has cut out a few times, and the idle varies fron strong to weak and surging, it's nowhere near as bad as it was. Good and bad, not bad enough to warrant a lot of poking and prodding (might make matters worse!), but not good enough to feel it's completely cured! Time to try the O2 disconnect maybe.

While I was looking for a solution I did read the thread about bigger injectors. Id like to get mine running correctly with the standard setup first and then maybe look for a bit extra.

Regarding your biggger injector setup. My understanding is that these engines run very lean in closed loop conditions but richer in open loop (>4000rpm). With the O2 sensor disconnected the closed loop phase (say <4000rpm) will revert to an open loop 'map', and the open loop phase will remain as before. A bigger injector will give a richer mixture throughout. But...what is the AFR <4000rpm without the O2 sensor, would a bigger injector make this too rich, and... if the closed loop operation was OK as standard wouldn't a bigger injector be over-richening the mixture? Do you know what AFRs were achieved by the standard injector with the O2 sensor disconnected and the new ratios with the bigger injector?
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