rNineT - idle problems - suggestions?

rNineT - idle problems - suggestions?

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Discussion

phatmanace

Original Poster:

672 posts

216 months

Sunday 16th July 2023
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My 2018 RnineT has developed an intermittent fault that causes a rough idle. I get an engine warning light on and and low speed the engine wants to idle at super high revs. If you let go of the throttle totally, then the idle is really 'rough' and the engine seems to 'hunt' between very low and very high idle. Riding at more than about 40mph is ok, although any low speed stuff when the problem happens is horrific as the bike lurches around.

Turning the bike off and on again seems to fix the problem (at least for a while), which makes me think it's either a faulty sensor, or maybe even something with the ECU.

Because it doesn't happen all the time, the normal place I take my bikes to be serviced couldn't make it occur and thus couldn't diagnose the fault. I therefore turn to the PH hivemind to see if anyone has a suggestion on what it might be (or where I might investigate next)

As it happened today when I was out for a ride, I recorded a small video which probably better explains

Video Here

X27

49 posts

172 months

Monday 17th July 2023
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Any form of hunting would make me think sensor (lambda maybe) or a spark plug issue. Good luck getting it sorted.

AceOfHearts

5,852 posts

198 months

Monday 17th July 2023
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I think you will probably have to take it to BMW and get it plugged into their diagnostics, otherwise you will end up throwing parts at it and spending a fortune.

Its most probably something like a throttle position sensor playing up, but without properly diagnosing its total guesswork.

Steve Bass

10,364 posts

240 months

Monday 17th July 2023
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Get a GS-911 diagnostic tool from Hex. Saves you the trouble and expense of getting t a dealer, especially if it's a simple sensor failure

black-k1

12,177 posts

236 months

Monday 17th July 2023
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Steve Bass said:
Get a GS-911 diagnostic tool from Hex. Saves you the trouble and expense of getting t a dealer, especially if it's a simple sensor failure
Definitely this.

OutInTheShed

9,381 posts

33 months

Monday 17th July 2023
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Water in the wiring caused a car of ours to do this.

Other things which spring to mind are:
Failing crank/timing sensor.
Dirty injectors
Dirty fuel filter.
Induction air leak
Sticking throttle

tinhead

100 posts

239 months

Monday 17th July 2023
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phatmanace said:
Turning the bike off and on again seems to fix the problem (at least for a while), which makes me think it's either a faulty sensor, or maybe even something with the ECU.

Because it doesn't happen all the time, the normal place I take my bikes to be serviced couldn't make it occur and thus couldn't diagnose the fault. I therefore turn to the PH hivemind to see if anyone has a suggestion on what it might be (or where I might investigate next)

]
Shouldn't matter if they couldn't make the fault happen, there will be a stored code if the check engine light has been on, as others have said get a code reader or take it somewhere who can read the code, otherwise its just guesswork.

Krikkit

27,000 posts

188 months

Monday 17th July 2023
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tinhead said:
Shouldn't matter if they couldn't make the fault happen, there will be a stored code if the check engine light has been on, as others have said get a code reader or take it somewhere who can read the code, otherwise its just guesswork.
Not necessarily if it's an intermittent fault, depending how they set up the mapping they're not always stored.

tinhead

100 posts

239 months

Monday 17th July 2023
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Krikkit said:
Not necessarily if it's an intermittent fault, depending how they set up the mapping they're not always stored.
With my triumphs a confirmed fault will simultaneously light the MIL and store a DTC in the ECM, unless cleared with software the MIL will only clear after 3 no fault heat cycles and the code only after 40 cycles.
There are only a few DTC's where the light will clear straight away but even then the code is still saved.

I've no experience of BMW's but assumed all bikes would be similar, no point showing the MIL if there is nothing to tell you why its on.

Biker9090

1,138 posts

44 months

Tuesday 18th July 2023
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Just buy an obd2 scanner and the motoscan app

airsafari87

2,861 posts

189 months

Tuesday 18th July 2023
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Slightly different issue to yours, but my V4 Aprilia used to hunt for revs after ticking over for a few minutes.

The throttle bodies needed balancing which cured the problem.

Not sure if something g similar on a BMW would throw the engine lights etc … that you’re seeing? But it might be worthwhile checking out?

Vantagemech..

5,733 posts

222 months

Friday 21st July 2023
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I see youre in Kent, I've Motorscan along with the associated dongle and loom, on the Kent / East Sussex border.
Whats the mileage, service history and the last thing to be done on the bike?

phatmanace

Original Poster:

672 posts

216 months

Friday 17th November 2023
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To cap this thread off, I got the bike fixed over the last couple of days, it turned out to be the exhaust servo - the flap was totally seized.

Thanks all for the help!

Jakey123

242 posts

152 months

Sunday 19th November 2023
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tinhead said:
With my triumphs a confirmed fault will simultaneously light the MIL and store a DTC in the ECM, unless cleared with software the MIL will only clear after 3 no fault heat cycles and the code only after 40 cycles.
There are only a few DTC's where the light will clear straight away but even then the code is still saved.

I've no experience of BMW's but assumed all bikes would be similar, no point showing the MIL if there is nothing to tell you why its on.
My gen2 Tuono would come up with errors but after a key cycle the code cleared along with the fault.
I would imagine an Rninet to have more advanced (AKA complicated) diagnostics though, German innit. They love to overcomplicate things, great when they work... just they don't for long.