GS-911 and ezCAN User Forum
General Category => Technical => GS-911 => Engine related issues => Topic started by: mike d on July 26, 2020, 06:31:58 PM
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Hi all,
Trying to help out a club member here in the UK. R1200GS 2007.
Symptoms/Actions:
No stored fault codes.
He took it out for a ride on Wednesday; trying to filter in traffic, it was borderline unrideable, not wanting to pull below 3,000 in any gear. In addition, when pulling up it was cutting out after a few seconds, even when fully warm.
I've been doing further investigation, and found that the lambda sensors were showing radically different values; sensor 2 was generally showing low voltage, indicating that cylinder was running very lean. I swapped the two sensors over to check it wasn't a faulty sensor, and it wasn't. Using a little throttle to keep the revs up a bit, it repeatedly stumbled; each time, the voltage dropped on sensor 2.
Swapped the primary coils over; it made no difference, either to the rough running or the difference between the two lambda sensor outputs. I also checked the TPS, which is fine – 0% on closed throttle, immediately registering any movement, and going up to 100%. Just running it on the drive, I got it up to temperature; it would then idle pretty happily at 1,200. I noticed that if I then gave it just a little throttle – enough to take it to 1,500 – it was then very rough, fluctuating to below 1,000 as it came close to stalling. Given more throttle, it seemed okay.
He found a slightly tight exhaust valve clearance, but even after correct adjustment, the bike still runs rough.
The bike has a full Remus exhaust system and no exhaust flap fitted,
Adaptations have been reset.
I have attached his initial .CSV file (M BUCK 1) with limited sensors. The file is a log of – TPS, RPM, injection time, lambda sensors – running it on the drive, including steady idle, steady at 2,00 and above, and the stumbling/rough running between the two.
He also sent me a file with all sensors shown, but it is in XLSX format, which I can't load on the forum.
I still think it could be a faulty Throttle position sensor.
All suggestions gratefully accepted.
Thanks
Mike
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Most likely a stuck idle bypass valve. Swap them over and check whether the symptoms move.
If they do, replace the one on the lean running cylinder.
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Update time (Members own words), plus attached file
I have made some progress, though it's still not completely okay. Yesterday I went over it again, and found that at least one of the pipes that links airbox to throttle body wasn't seated at the airbox end. That pain was self-inflicted; when reassembling, in place of the BMW clips I used jubilee clips. Those are wider than the BMW clips; they work fine on both ends of the throttle body, but the extra width is a problem on the airbox end. I think that, when I tightened everything up 'just to be sure', it had actually pulled the pipe off. I've now removed the jubilee clips at that end and reseated the pipes, and on a brief test ride it didn't feel like the bike was actively trying to kill me!
It still won't idle when cold, and still runs rough just off idle. Following your email this morning, I swapped over the idle valves, which made no difference to the behaviour or the lambda output values. The attached is from this morning; it needed throttle to start (lines 16 to 23), and then settled to a fairly smooth idle around 1,200 (lines 24 to 51). Take a look at lines 65-ish to 75; on a small throttle setting, that's when it runs rough, the revs fluctuating between 1,600 and 1,000. From line 80 to 133 I used a steady throttle to keep the revs around 2,000; that's when lambda 1 is continually reading high (rich), while lambda 2 is oscillating between rich and lean.
Mike
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The fact that you need to twist the throttle to get it to start tells me that one (or both) of the idle bypass valves isn't working. Although the readings on you csv file indicate that they are working, have you physically removed them and cycled the ignition to watch whether they actually move in and out as they are supposed to?
This is what they should do when cycling the ignition. First click you hear is ignition on, second click is ignition off.
[youtube]https://youtu.be/C7dJqVwOCsw[/youtube]
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It would be nice to see a full set of data.
The lambda voltages oscillate between 100 and 900 mv the samples that your data is showing can not give any information as the sample rate is slow, and the points can be picked any where from the wave form.
Best to use the GS911 and look at the wave form.
The lambda control factor readings would be more interesting along with Injector pulse width ,Air temperature, Engine temperature, Throttle position etc.
If you publish a full set of data, listing the point at which the problem is occurring, I would like to take a look at it.
No guarantees, just interested.
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Hi Chris,
Do you want it in graphical format or numeric?
Mike
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Just the .CSV file with a full set of parameters would be good.
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From previous .csv file the idle actuator readings look a little bit low at idle and the rpm looks a bit high. Are the blanking rubber caps still on the vacuum ports? and also no one has adjusted the throttle valve stop screws?
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The following response is again from the member (I am miles away from the bike), see the attached CSV file that is associated with this post:
I've done my best, though it's not a FULL set of data due to that hammering the refresh rate. There are two worksheets in the attached spreadsheet, one where I captured the bare minimum, the other where I captured most of the 'dynamic' settings. Engine temperature was 100-105 C; it was reporting ambient air temperature as 27C, which is around 10 degrees higher than it actually is. I think that's probably due to hot air coming off the engine.
Both sets of data show the same thing, that when using throttle to maintain around 2,000 rpm, lambda 1 stays continually rich while lambda 2 bounces around, anything from 50 to 70 up to the 800s. This time, I spotted that there's quite a difference between the two knock sensors as well. I'm not sure what else is significant in the data. The sampling rate is still low, no more than three samples per second; that was with it set to 'turbo' sampling rate. Is the sampling rate a function of the speed/power of the computer being used, as well as the number of data items being sampled?
Both blanking caps are still in place. I don't even know where the throttle valve stop screws are, so I doubt I've adjusted them!
He has an appointment with the local BMW main dealer today, so whatever is found I will report back.
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Just had a quick look. will look in greater detail later.
The lambda sensor in column C at 2000 rpm is reporting an air fuel ratio of a constant 11 to 1 this is very rich whilst the other sensor looks right at about 14.7 to 1.
So first I would swap the sensors over.
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The sensors have already been swapped, fault remained on the same side (see first post).
Mike
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You could try unplugging that sensor as I understand the ecu would default to a reading of lambda 1 = 14.7 to 1 AFR
As the ECU is seeing a rich reading of 11 to 1 on one cylinder it will try to lean that cylinder out.
The output signal for the injector pulse width is common to both cylinders so unless that injector is faulty they should be even.
Try swapping the injectors over.
Obviously the throttle position sensor is common to both cylinders.
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Lambda sensor readings are a reflection of what is happening to the combustion and fuel mixture, not the cause of the issue. Replacing a lambda sensor because it is giving a rich reading is like running a fever and then tossing out your thermometer because it is giving you a high temp reading. :o
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I agree Lambda sensor readings are a reflection of what is happening to the combustion and fuel mixture.
But It seems to be a faulty sensor reporting a rich mixture to the ecu, or a rich mixture being caused by a faulty injector being reported to the ecu by a good lambda sensor.
As it appears on only one cylinder I can not see anything else that is not common to both cylinders that could make that much difference to the AFR`s of one cylinder.
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I have suggested replacing the idle actuators but it would appear that 12 years of experience on these bikes doesn't count for much.
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I would say 12 years experience counts for an awful lot and for me everyday is a school day I am only trying to help and learn at the same time.
I am missing something the idle actuators are the same readings although I realise that there is no feed back loop to the ecu to tell the ecu their position.
But according to the data and the op the idle is fine, the problem is at 2000 rpm when one lambda sensor is reporting a rich mixture of 11 to 1 and consequently the ecu is leaning out the mixture.
Hence the injector pulse width is less at 2000 rpm with 2% throttle than at idle with 0% throttle.
As I said earlier I thought the idle actuator position looked a little low at 75 steps at idle I would normally expect to see around 116 steps.
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Hi Jughead, Chris,
Thanks for your contributions thus far.
He swapped the idle actuators over, and also removed them to test as you suggested, they were operating as per the video clip.
I fully agree with your statement :
Replacing a lambda sensor because it is giving a rich reading is like running a fever and then tossing out your thermometer because it is giving you a high temp reading.
And that's also not what the owner was suggesting. He was looking to understand what was not common to both sides, the injectors have been swapped.
He has a long riding holiday planned in early August, so was trying to get it sorted before then. He had an appointment with the local BMW main dealer today, but I've not heard back from him yet on what if anything has been found.
I will report back on on the findings.
Regards
Mike
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Hope he gets it sorted, it will be very interesting to see what the problem was. :)
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Latest episode ;D
There was good news and bad news from the visit to North Oxford today. The bad news is that they haven't been able to track down the problem, or cure it. The good news, part 1, is that I persuaded them to pull the TPS from a used RnineT and try that. It didn't work, but at least that's one component ruled out. The other good news was that they only charged me for an hour's labour, when I suspect they spent more like two hours on it.
Initially, they claimed they had seen suspect data from the TPS: just off a closed throttle, they reckoned it jumped to 100%. That's something I've never seen with the GS-911, and it doesn't fit with the behaviour; if the ECU thought the throttle was wide open, it would instruct the injectors to dump lots of fuel in, which would then make it run catastrophically rich since the butterflies would still be shut. Also, since there's only one TPS, any issue with that would affect both cylinders equally.
So I'm a little further forward. What I have found is that I can get two used lambda sensors, plus two throttle bodies – complete with idle adjusters, injectors and a TPS – from James Sherlock for less than £90. So they should be with me by the weekend. If the problem is still there after changing that lot, I will be completely stumped as to where to go next!
Mike
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I too would find their TPS finding dubious, normally the track gets dirty although I have seen a wiper come adrift giving an 85% reading at closed throttle showing an injector pulse width of over 10ms when trying to start the bike, it was swamped with fuel but of course it was on both cylinders.
Good luck with the replacement parts it will be interesting to see the results.
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Not only do I find the TPS suggestion strange, but apparently they didn't mention finding any issue with lambda sensor readings.
Latest update from Martin:
If they saw the unusual lambda readings, they didn't mention it, and I forgot to ask. I doubt they swapped the coils, either, since swapping the TPS had clearly not occurred to them until I mentioned it.
The throttle bodies came today, which was ultra-speedy, though not the lambda sensor; because it's all on ebay, they're separate orders. I've now swapped the idle actuators (and remembered to run the adjustment routine), the injectors, and the TPS (remembering to do the re-learn routine) and none of it has made any difference; it still stumbles like a drunkard just off idle. Here's hoping the lambda sensors sort it out – I'm running out of bits to replace!
Mike
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Was there ever a resolve to this problem.
If so an update would be good to store away in the brain cell for future use.
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Hi Chris,
The story's not finished yet.
The last work he did was to make a manometer (I was going to send him one), and check the throttle body balance.
Well, the bike has me completely flummoxed. I spoke to an independent specialist BMW mechanic; he said that my description of it stumbling just off idle was consistent with the primary coils breaking down. So I ordered a pair of new coils, plus a pair of used secondary coils; they made no difference whatsoever.
I put together a DIY vacuum gauge using lengths of clear plastic tubing and automatic transmission fluid; the bodies were considerably out of balance. They are now balanced at 2,000 rpm and above, though there's still a difference at idle. That's made it run a little better, but hasn't resolved the problems of it refusing to idle when cold, and stumbling/running rough between idle and 2,000 rpm.
He went on holiday yesterday, so a full update will be posted on his return.
Regards
Mike
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I will keep an eye on this post.
Regarding balancing, of the several sets of carb balancers I have I prefer the Morgan Carbtune Pro, with the steel rods.
I tend to balance the carbs at the point when the throttle butterfly`s are just starting to move, I feel that if they are right at this critical point then the difference at 2000 rpm and up wont make that much difference.
It would be nice to have them perfectly balanced all he way through but with the cables and plastic junction box that is not going to happen.
At the end of the day this does not account for the data reading on the one lambda sensor being wrong.
It is a shame that the AFR can not be measured on each cylinder just to confirm the data.
I guess I am spoilt having welded extra ports in the headers to take wide band sensors and using an Innovate LM2 to monitor AFR .
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Hi Chris,
I run the tool hire facility for the BMW Club (UK), and we also have a couple of Carbtune Pro's, which is what I offered to the member. Good piece of kit.
Mike
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If he is confident the idle actuators are working 100% as they should, he could check the plastic clip/cover behind the throttle bodies. If they are not seated correctly, it could also create an imbalance in the bodies. Both cables MUST have a small amount of freeplay when the throttle is fully closed.
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Hi Jughead,
Thanks for the suggestion, I'll pass it on for when he gets back rom holiday.
We have been shielding since mid March, but are now allowed visitors etc, so it may be possible for him to ride over to my place as he is about 50 miles away.
Mike