K1200RS - No power on decellerating thru 5000rpm - K-Bikes.com - Excellence in Motion
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post #1 of 30 (permalink) Old Nov 14th, 2005, 5:00 pm Thread Starter
 
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K1200RS - No power on decellerating thru 5000rpm

Hi,
I have a 2001 K12RS.
When I close the throttle slightly and the revs drop, the power cuts abruptly at 5000rpm. If I continue to decellerate the power comes back on at about 4700rpm. If I open the throttle the power cuts back in sharply at 5000rpm. It feels like the fuel is completely cut off.
It does eactly the same in every gear at exactly the same revs, irrespective of the throttle setting.

As you can imagine, this is a bit unsettling when adjusting the power in a corner in second gear - its like slamming the throttle shut.

The dealer doesnt know what the fault is. He replaced the lambda sensor (which was out of spec) but it made no difference. I have a feeling I'm going to be throwing money at him while he guesses which expensive part needs replacing.

Has anyone had the same problem?
Does anyone know why?

Thanks
Matt
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post #2 of 30 (permalink) Old Nov 14th, 2005, 6:42 pm
 
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ecu

Quote:
Originally Posted by matthassock
Hi,
I have a 2001 K12RS.
When I close the throttle slightly and the revs drop, the power cuts abruptly at 5000rpm. If I continue to decellerate the power comes back on at about 4700rpm. If I open the throttle the power cuts back in sharply at 5000rpm. It feels like the fuel is completely cut off.
It does eactly the same in every gear at exactly the same revs, irrespective of the throttle setting.

As you can imagine, this is a bit unsettling when adjusting the power in a corner in second gear - its like slamming the throttle shut.

The dealer doesnt know what the fault is. He replaced the lambda sensor (which was out of spec) but it made no difference. I have a feeling I'm going to be throwing money at him while he guesses which expensive part needs replacing.

Has anyone had the same problem?
Does anyone know why?

Thanks
Matt
Matt:
It is a known problem. My 02 does it very repeatably. An informal poll at last May's RR Rally showed that it happens on RS and LT bikes. It will definitely cause you to soil your shorts under the right circumstances.

One person on this forum (cabnfvr) replaced the ecu on his 02 and it fixed the problem but that is an expensive proposition.

The 03/04 guys got ecu upgrades to fix other problems so I'm not sure if they ever saw the problem or if the new ecu fixes it. Us 02 guys are just so lucky!

Why does it do it? I believe it is a problem with the engine map in the ecu. For whatever reason at 5k rpm rolling off the throttle to nearly-closed the ecu cuts too much fuel out (or maybe all fuel) and the engine effectively dies. Once the rpm's drop a bit below 5k rpm the ecu gets to a point in the engine map where it is told to increase fuel. Just a theory, but else why do replaced ecu's fix the problem, as opposed to replacing O2 sensors, tps sensors, yada yada.

Mark
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post #3 of 30 (permalink) Old Nov 14th, 2005, 8:36 pm
 
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Red face Why the sudden fuel cutoff upon deceleration

Matt, the reason the sudden cutoff occurrs is related to a limitation of the linear range of the fuel injectors and the emissions legal engine calibration strategy of your model. In other words the fuel injectors cannot deliver repeatable flow below a minimum pulsewidth that would be required to continue delivering fuel under near closed throttle when manifold pressures drop and mass flow entering the cylinder is below the minimum fuel delivery threshold. The problem can be reduced with a reprogrammed performance chip from rhinewest and others. There is little your dealer can do with oem parts to resolve decel cutoff except verify all adjustments of the throttle slack and tps or to trade it for a newer model.

Hope this helps, Turbo

Last edited by turbocohen; Nov 14th, 2005 at 8:38 pm. Reason: left info out
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post #4 of 30 (permalink) Old Nov 15th, 2005, 7:10 am
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Red face

Quote:
Originally Posted by turbocohen
The problem can be reduced with a reprogrammed performance chip from rhinewest and others.
San Jose BMW has been installing Power Commanders on our bikes for a few years now and I'm wondering if anyone out there has been able to correct similar problems that you and I are having with one of them?
I've been chasing down the same problem on my 98 KRS and so far I've replaced the O2 & Air sensors that have helped out alot but the problem is still there when I closed down the throttle slightly, usually while I'm going downhill in the Mt's setting up for a turn.
I'm not sure what else I can do at this point other than go with a P.C. and put it on a Dyno and make a new map for it.
The price for a new chip or a P.C. are about the same but I'd still have to pay the for the Dyno time if I choose to make a custom map.

Jerry
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post #5 of 30 (permalink) Old Nov 15th, 2005, 7:41 am
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Quote:
Originally Posted by matthassock
Has anyone had the same problem?
Matt, check out this thread from the old board. Sometimes the TPS (Throttle Position Sensor) needs to be adjusted, as "turbocohen" has stated above. Specifically, Message No. 63527 in the thread. HTH
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post #6 of 30 (permalink) Old Nov 15th, 2005, 8:20 am
 
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pw

Quote:
Originally Posted by turbocohen
Matt, the reason the sudden cutoff occurrs is related to a limitation of the linear range of the fuel injectors and the emissions legal engine calibration strategy of your model. In other words the fuel injectors cannot deliver repeatable flow below a minimum pulsewidth that would be required to continue delivering fuel under near closed throttle when manifold pressures drop and mass flow entering the cylinder is below the minimum fuel delivery threshold. The problem can be reduced with a reprogrammed performance chip from rhinewest and others. There is little your dealer can do with oem parts to resolve decel cutoff except verify all adjustments of the throttle slack and tps or to trade it for a newer model.

Hope this helps, Turbo
Turbo:
If that is the case, why does it not happen at all at 6k rpm or 4k rpm, only at 5k rpm? If it were an injector open-time resolution problem it would always happen, certainly at rpms just above and just below the magic 5k. Also, since the pulse width is a minimum at idle and the bikes idle fine, I would assume any pulse width greater than that should be achieveable and certainly such a pulse width at 5k would keep the engine running when the throttle is suddenly closed.
Mark
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post #7 of 30 (permalink) Old Nov 16th, 2005, 2:33 pm Thread Starter
 
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Thanks for the good advice. The bike goes in for its 36000 in a couple of weeks.
I'll let you know what transpires
Cheers
Matt
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post #8 of 30 (permalink) Old Feb 17th, 2006, 4:50 pm Thread Starter
 
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Problem Fixed!

Hi
I said I'd come back when the bike had been serviced.
The bike came back from the shop yesterday. They had replaced the TPS and the throttle cables during the service. The problem was exactly the same.

They took it back and kept it for a week (I think they may have had a guy from BMW UK look at it). They finally replaced the ECU which fixed the problem. BMW would not do a warranty replacement so the unit cost around 550 (uk pounds). The shop cut me a good deal on the labour charge though so it wasn't as bad as it could have been.

I gotta say - the bike goes GREAT now. It had been bad for so long I had forgotten how good it used to be. I can use the whole rev range now and it's like a rocketship. So I'm glad I got it done. I don't want a K1200GT so bad now.

Cheers

Matt
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post #9 of 30 (permalink) Old Feb 18th, 2006, 1:45 pm
 
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new ecu

Matt:

I'm glad your bike is running the way it should. It must be awesome.

I have to say that it is unfortunate that BMW is profiting from a defective ECU installed on pre-03 bikes. I don't understand rewarding their incompetence by purchasing a new ECU for $958, or for that matter, for any amount.


Mark
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post #10 of 30 (permalink) Old Feb 18th, 2006, 3:43 pm
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Why does my '97 go like a train and not seem to suffer any of these problems? Am I just lucky or perhaps I don't give it enough stick?

The only problem I've encountered was after a long high speed sustained cruise, then slow urban ride, the idle rpm was running a bit higher and slightly erratic. Didn't come back when the bike was parked up and run again. Since the 150mile cruise went like a dream, I didn't worry much about the last few miles.



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