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post #1 of 23 (permalink) Old May 9th, 2013, 5:56 am Thread Starter
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Question RS drops to low idle RPM's

Hi! My name is Laurens van Deijk, from Holland & since recently owning a '99 K1200RS.
Bike is giving me mixed feelings. The handling is outstanding, it's reasonably quiet & delivers enough performance for those long trips.

Since a month or so it seems that there has developed a problem when I drop to idle. Instead of dropping to 1000/1100RPM, it drops to 600/700RPM and afterwards the computer picks it to regular values. I asked my local dealer (BMW specialist) to take a look at it. Moditec values looked good, but the idle behaviour was still there. They manually tweaked the TPS a bit. Altough the idle behaviour was still there it felt a bit better.

I did some online research. Symptoms seem to be related to air leaks etc. This morning I took off the fairing & inspected the intake manifolds & the gashousing (don't know the correct english word ). Looks ok. No tears & dry spots. Sprayed of good bit of brake cleaner while the bike was running & warmed up. Could not notice any difference in idle speeds. Afterwards I took off the tank & inspected the air filter. Few flies here & there but it looked fine. Put everything back & went for a testrun down the neighbourhood.

Dropping below regular idle speeds seem to be less when riding without fairing (could be my imagination...).

I need some help determing the next step. This weekend I'm going back to the dealer for another TPS checkup. Althought I'm not a skilled technician in any way I'm not a complete idiot. Can take everything apart if I understand how it works, just takes a lot of time.

P.S: been a while since I wrote anything down in English, excuse me if some things don't make sense...
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post #2 of 23 (permalink) Old May 9th, 2013, 8:12 am
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You are looking at all the correct things. I had a similar problem some years ago, usually when the engine was hot in cities.

Make sure the engine breather hoses are OK and not split. I found 2 from 3 inlet stubs (intake manifolds) were not true flat when I checked them on a glass plate. I made them true and replaced all the O rings.

Then I replaced the O2 sensor in the exhaust and all has stayed good. Did they check the O2 sensor on their Moditec? If it has been in the bike for a long time, it may be worth replacing it anyway.

If your problem is like mine, then it is NOT the ECU but a problem with the Efi loop not compensating mixture at idle or responding too slowly. Check the simple things first. Part of the TPS throttle rail is an idle switch which kicks in then the throttle is at the idle position but the Moditec should have picked up a problem if that was faulty or not properly adjusted.

Have you tried a TPS reset? Leave battery disconnected for an hour, reconnect then key on and roll the throttle fully forwards and back a couple of times before starting.



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post #3 of 23 (permalink) Old May 9th, 2013, 9:38 am
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Flies on the air filter? They can get pretty big, mushy and sticky up here.....was getting tired of that and screened my air intake after pulling too many of them out of the bottom of the air box/top of the filter. Much better and will extend the life of my air filter. Cheapo me used a piece of aluminium mosquito screen shaped around the intake and a zapstrap.

OK....my bike only once had problems similar to yours. A tank of gas from some place in the boonies did that. Fixed with fresh gas and a TPS reset roadside. But I also had a plugged filter recently at less than the "recommended" replacement schedule. Had different symptoms following that but left unchecked, I am sure symptoms maybe similar to yours could have happened or even worse may have burned the fuel pump.

Manual TPS reset/tweak from a dealer??? Sounds iffy there should be a procedure for that and if the BMW procedure is anything like the GS911, may take more than a manual tweak. But in any case if the TPS is outside its settings or defective it should give a fault code. At least it does with the GS911.

Binding or loose throttle plate? Worth looking at, one of mine was loose and starting to bind from the marks on the throttle body. That kind of terrified me just thinking that my engine could have swallowed one of them screws. Someone else found the same on his bike. I think you can look from the top of the air box with filter removed and somehow inspect that. May need a long screwdriver and maybe even a flex one if just to reach the screws and make sure they are tight.

Also the brake cleaner....I wouldn't use that for leak tests. It can, depending on the formulation attack wire casings or other plastic parts. May not look like it does at first but they may just crack later. Yep been there...

I just did my bike if just for a quick recheck of my O-rings intakes and hoses after a couple years. I used a cheapo vacuum gauge connected to each port in turn and compared the readings. Also did it with my 4 columns manometer....all checks out good, no strange fluctuations of the columns or needle that could indicate a vacuum leak or worse a burnt valve.

Single vacuum gauges are cheap and a quick/safe way to check for leaks. But all of them come with an unrestricted hose unless they are moto specific. If you choose that for diagnostics you will have to restrict the hose somehow. I just used a pair of pliers to squeeze the hose until the needle stabilized.

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post #4 of 23 (permalink) Old May 9th, 2013, 10:43 am Thread Starter
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Quote:
Originally Posted by voxmagna
Make sure the engine breather hoses are OK and not split. I found 2 from 3 inlet stubs (intake manifolds) were not true flat when I checked them on a glass plate. I made them true and replaced all the O rings.
Where can I find the engine breather hose?

Quote:
Originally Posted by voxmagna
Then I replaced the O2 sensor in the exhaust and all has stayed good. Did they check the O2 sensor on their Moditec?
Hmmm, not sure. Will check with them this weekend.
Moditec is able to report all sensor faults?

Quote:
Originally Posted by voxmagna
Have you tried a TPS reset? Leave battery disconnected for an hour, reconnect then key on and roll the throttle fully forwards and back a couple of times before starting.
Haven't heard of this one yet! I turned on the lights, opened up the throttle 3 times & turned everything off. I thought this was the correct way to reset the TPS?

Quote:
Originally Posted by H96669
OK....my bike only once had problems similar to yours. A tank of gas from some place in the boonies did that. Fixed with fresh gas and a TPS reset roadside. But I also had a plugged filter recently at less than the "recommended" replacement schedule. Had different symptoms following that but left unchecked, I am sure symptoms maybe similar to yours could have happened or even worse may have burned the fuel pump.
I'm sure it's not dodgy fuel. Have been at the gas station for 10 times after.
Here in the Netherlands the standaard is Euro95 (octaan 95).

Quote:
Originally Posted by H96669
Manual TPS reset/tweak from a dealer??? Sounds iffy there should be a procedure for that and if the BMW procedure is anything like the GS911, may take more than a manual tweak. But in any case if the TPS is outside its settings or defective it should give a fault code. At least it does with the GS911.
That what I thought. Basicly they adjusted something as a workaround for the real issue.
It's hard for me to explain what they did exactly. After setting it correctly on the Moditec they noticed during the testrun that it still dropped erradicly, so the tech made manual adjustments to the gashousing.

Quote:
Originally Posted by H96669
Binding or loose throttle plate? Worth looking at, one of mine was loose and starting to bind from the marks on the throttle body. That kind of terrified me just thinking that my engine could have swallowed one of them screws. Someone else found the same on his bike. I think you can look from the top of the air box with filter removed and somehow inspect that. May need a long screwdriver and maybe even a flex one if just to reach the screws and make sure they are tight..
Not quitte sure that I understand what you mean. Could you show it on a picture?
http://www.realoem.com/bmw/showparts...43&hg=13&fg=71

Thank you both for your replies!
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post #5 of 23 (permalink) Old May 9th, 2013, 5:40 pm
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The engine breather hose is sat right on top of the motor. You can just about see it through the frame with a flashlight. It goes brittle, cracks and often lets blow back oil leak over the motor (from the top).

If you are seriously going to go looking for possible faults yourself, rather than postulate this or that then you will have the tank and air box off the bike and be able to get a better look at the breather hose assembly.

At this stage with the fault you describe, I would not even let a dealer near the TPS and throttle rail to fiddle about with settings that could be very difficult to get right or make things worse by masking the real fault. You say they said 'workaround'? that is exactly what I mean - they add another layer of uncertainty which may make finding a solution more difficult.

The one good thing about these bikes is if you do not mess or let others mess with factory settings they stay pretty stable. The EFi is a feedback loop and when something is not right it usually means a component is faulty, out of tolerance or something fundamental is wrong. In your case I am pretty sure the mixture balance at idle is outside the range which the Efi loop is trying to correct when you roll off the throttle. Either that or the Efi loop is responding too slowly to changes.

Brake cleaner may be totally the wrong thing to use for leak and mixture exploration. If it is the older flourocarbon type, it may not be too friendly towards your O2 sensor! I have used propane gas, but you need to think about a safe system of work before using it and setting fire to your bike!

There is one setting of the TPS that they can do far easier with Moditec or a GS911 and that is the TPS zero reference (which is not actually 'zero' but an offset voltage). Before they start messing with that they should make sure there is free play in the throttle cable and the throttle rail is right back at the idle stop.



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post #6 of 23 (permalink) Old May 10th, 2013, 9:25 am
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Sorry I am in probably the worse place to either post pics or open links on RealOEM. "Internet at Sea".....sucks, won't even let me put on smilies.

OK throttle plates, that's the brass "flappers" inside the throttle bodies. You can see them looking from the top of the airbox down. Each is secured to the throttle shaft with 2 screws, that's pretty standard on all carburators and FI systems. Just in case check them screws, you do not want your engine to eat one of them if it does come loose, that would be catastrophic to say the least.

If I can I'll post pics but may take a few days. Pics where you can see one of the throttle plates starting to wear out the bore of the throttle body and bind, altough on my bike that wasn't causing any idle problems....just yet.

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post #7 of 23 (permalink) Old May 10th, 2013, 12:58 pm
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If he starts with the throttle body mixture screws set as they left the factory and all in the same position, the idle vacs will be all over the place if there was leak through the spindle shafts and the same is true if a butterfly flap is not closing off properly.

This is an interesting area for the ECU because it will try to correct the idle mixture by taking an average of all 4 throttle bodies. The closer the bodies are giving consistent mixture, the easier will be its job. Now we know from some good recent posts that the idle actuator control is believed to work between 2 voltage extremes. Logically, if that valve is operating around its control center and changing when mixture is artificially changed, then the ECU has good control. But this is getting into some heavy Efi system management.

Whilst adjusting mixture screws a tad may even up the vacs to make idle a bit smoother, it does nothing for the idle rpm. The ECU has that programmed in and if the correct idle is not achieved with the throttle rails settings as per factory, the conclusion must be that the mixture is so far out the ECU cannot control it.

If you watch the switching response from the O2 sensor, you can do some interesting things with propane gas injection provided you take precautions.



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post #8 of 23 (permalink) Old May 17th, 2013, 4:30 pm
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So, my '00 is acting in a similar manner. What I am experiencing is either a high idle or a low idle. When I first start the bike cold, it idles fine, once warm and after riding, it will either be high at about 1500-1800 rpm, or it will drop to the 7-800 rpm and sound like it is about to break. I add a tad throttle and all is well until I let off. It will sometimes come back down to the proper rpm. It sat somewhat unused for the better part of three years while I had my fun with the K1300S. Now the RS is the primary bike. I also sprayed brake clean into the throttle body area with no change noted. Since mine seems to be temperature related, and it always had issues when it was raining, I was wondering if this might be related to the HAL sensor? The rain affected behaviour matched what others have said regarding that. I also had the TPS replaced for the high idle rev about 15,000 miles or 4 years ago. I suppose that could have failed again. Breather hose appears fine (last replacement was again 4 yrs ago and very little use since, no evidence of blow by gases or oil deposits on the top of the case - very familiar with this). So, Vox, is it possible it is related to the HAL?

Have not done the throttle reset, will try that tonight.

Jim Douglas
'00 K1200RS >135,000 mi, '09 K1300S sold @ 22,232 mi
'93 K1100RS traded up @ 78,000 mi, '85 K100RS sold @44,000 mi, Kawi 650 track bike - sold
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post #9 of 23 (permalink) Old May 17th, 2013, 5:51 pm
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The Hall sensor is there to provide the sparks at the the right time. Unless you feel the motor is running rough at the very low idle due to missing sparks, I would say no.

There is a separate engine temperature sensor in the cylinder head that decides how cold the motor is. That tells the ECU to richen the mixture for cold starting and lean it off as the motor comes up to temperature. Obviously you should also be seeing normal KRS temperatures on the gauge.

As I said earlier.Efi systems only work when everything else in the system is doing what it expects within its range of control. I have already posted resistance figures (also sailor) for the head thermistor. You can check its temperature at ambient with a multimeter, But to do the full range it is best removed and tested in an oil bath over the stove.

My first guess would be the TPS itself, but you said you had that changed and mine has done 45K miles since 1997 no problems. The TPS is a double potentiometer (like a radio volume control). It has carbon tracks which wear most at the first 1/4 throttle end. The tracks can get pitted or develope 'holes' which causes the voltage signal to fluctuate. It is this voltage signal that is the 'throttle' signal for the ECU. I am pretty sure the GS911 could show up a TPS track error. You definitely do not want to be getting brake cleaner near/inside the TPS module!

Your bike has sat unused and the TPS signal quality is very important. As a first shot I would buy a can of electronic switch cleaner from RS components (or Tandy?). I use the 'Electrolube' brand switch contact cleaner if you have it. Lift the tank and throughly clean the connectors to the TPS and the big ECU connector. In fact, separate every single connector you can see, look at both ends carefully for weather tarnishing with an eyeglass, give them a good dose of switch cleaner, then plug and unplug them a couple of times to clean the pins.

I am suspicious your first problem really was the TPS. You could have had poor connector contacts and replacing it with new seemed to fix the problem which was really on the connector mating half or the wiring still with the bike.

The same is also true of the O2 sensor connector which again could have bad contacts.

The engine temperature sensor at the back of the cyl. head also has a connector.

Don't assume anything. When you next have the tank off, re-check the breather hoses, throttle bodies and air box ducting for any signs of leaks.

If you can get the fault to keep coming on regularly you could also consider getting a diagnostics check done. Bear in mind diagnostics MAY hit the right area, give you some pointers as to where to start looking, or could take you somewhere in the system when something else is the real problem.



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Last edited by voxmagna; May 17th, 2013 at 5:57 pm.
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post #10 of 23 (permalink) Old May 18th, 2013, 5:45 pm
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Thanks for the tips. I have to pull my suspension tomorrow so, I might as well get going on this as well.....three years dormant and the rebound damping is nonexistent in front...
Thanks again...oh, and just before the TPS was replaced by the dealer, I replaced the O2 sensor myself on their advice though, admittedly they said they were guessing based only on my verbal descriptions....Time to go ahead and get that 911.
Thanks again!

Jim Douglas
'00 K1200RS >135,000 mi, '09 K1300S sold @ 22,232 mi
'93 K1100RS traded up @ 78,000 mi, '85 K100RS sold @44,000 mi, Kawi 650 track bike - sold
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