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Update on back/afterfiring


Bugs

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I promised a number of you that I'd get back to you on the resolution of the back/afterfiring problem I had on my '05 R1200RT.

 

Yes, I know it's been a looong time since I first posted this issue, but it's not because I forgot to check back in. In fact, both BMW and my local dealer had my bike in the shop for all this time... 4 or so months all tolled, trying to find a resolution. They tried everything from reprogramming the CPU, to replacing multiple throttle bodies, and seemingly everything in between. They even tried a number of the suggestions some of you on this site volunteered... but, no luck. I'm told the bike will soon be on its way back to Germany.

 

I missed a lot of riding this summer/fall, but BMW is stepping up in the end and has offered me a resolution I'm happy with going forward. Like I told them, the true measure of a man, or organizations of man, is not how they perform when things are going well, but how they perform after things don't go so well.

 

It will be great to get back on the road and back to complaining about things like tire wear and traffic.

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ShovelStrokeEd

As previously stated, T.A.D.T., even my CBR XX will grumble on the over run.

 

Glad you are coming to a resolution of the problem. Don't be surprised if the new one doesn't do more of the same.

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It`s a normal condition. Decel mode leans out the fuel mixture. The throttle body closes and you get a lean misfire condition. If it did`nt shut down the injectors you would continue to run at speed. dopeslap.gif

The replacement bike will do the same thing. eek.gif

Have fun. grin.gif

Cant fix it if it`s not broken. thumbsup.gif

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It`s a normal condition. Decel mode leans out the fuel mixture. The throttle body closes and you get a lean misfire condition. If it did`nt shut down the injectors you would continue to run at speed. dopeslap.gif

The replacement bike will do the same thing. eek.gif

Have fun. grin.gif

Cant fix it if it`s not broken. thumbsup.gif

As you seem to say, when the throttles close, the FI system shuts off the gas compeletely until the motor drops to around 2000 RPM. If this was NOT done, the result would be a very rich mixture. not a lean one.

 

The reason for this is that there is a minimum amount of fuel that the injectors are able to inject on each shot. The amount of air the engine is sucking in during each cycle when decelerating with a closed throttle is very minimal. The injectors cannot inject a small enough amount of fuel to make a correct mixture. The result is that there will be too much fuel for this tiny amount of air, and a rich mixture will result.

 

The end result of all this is that HC and CO emissions will skyrocket on closed throttle deceleration. The main reason why fuel injection systems cut off fuel when decelerating on a closed throttle, was emission-related. Cars (which are the major user of fuel injection systems) could not meet emissions requirements if one of two things were not done. This is one of them.

 

The other way to fix the problem, was what was done on carburetted cars: Use a dashpot to prevent fast closing of the throttle, so that the throttle was held slightly open when decelerating. This "solution" was a band-aid and was really annoying for the driver, so the fuel cutoff method was by far the best solution to avoid rich mixture during "overrun".

 

Bob.

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It`s a normal condition. Decel mode leans out the fuel mixture. The throttle body closes and you get a lean misfire condition. If it did`nt shut down the injectors you would continue to run at speed. dopeslap.gif

The replacement bike will do the same thing. eek.gif

Have fun. grin.gif

Cant fix it if it`s not broken. thumbsup.gif

 

Guys,

Do you honestly believe BMW would work on this thing for 4 months and give me a brand new bike if they thought it was a normal thing and that the very next bike they gave me would do the same thing? Do you think that my dealer who has sold and serviced hundreds of BMW's who tells me they have never seen this problem, who also tells me they have checked with numerous other dealers and have found that none of them have encountered this problem, would work on this problem for 4 months knowing that the very next bike they give me will do the same thing? Or, is it more likely that the problem my bike has demonstrated is, in fact, not the same issue you are thinking of when you say it is "normal" and will occur on the next BMW I own?

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btw, you may also find it interesting to know that in addition to trying two new sets of throttle bodies, several combinations of old and new, they also replaced the fuel injectors... no impact.

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ShovelStrokeEd

In fact it is very likely to do just that.

 

As First Beemer explained, although not very clearly or accuratly, on the overrun, the mixture goes very lean. This results in incomplete, or even missed combustion events. The subsequent unburned mixture is pumped into the exhaust system. The next true firing event can ignite this partial charge and cause the pop you here and feel. The reason the charge doesn't get to the end of the pipe is that its energy is considerably lower than the gases which have been heated by combustion and so tend to linger in the vicinity of the exhaust valve rather than rush out the tail pipe.

 

There are things which can be done to help alleviate this problem. A richer overall mixture will tend to do it less. Leaks at either the intake or exhaust system, in particular the exhaust, will tend to exacerbate the problem. Being certain that the fuel cutoff is actually working (TPS and ECU) are paramount.

 

I am sure a new bike will make you feel better, I doubt that the condition will be fully cured but it might be less on the new one.

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The reason for this is that there is a minimum amount of fuel that the injectors are able to inject on each shot. The amount of air the engine is sucking in during each cycle when decelerating with a closed throttle is very minimal. The injectors cannot inject a small enough amount of fuel to make a correct mixture. The result is that there will be too much fuel for this tiny amount of air, and a rich mixture will result.

Nonsense! How do you think the engine runs at idle speed?

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ShovelStrokeEd

The fuel actually is cut off based on a couple of parameters. Engine RPM > 2000 and throttle position sensor signal < 0.500 volts. Under those conditions the ECU will cut fuel to the injectors. It is brought back on once either of those conditions fails. This allows the motor to continue to run and return to idle state if needed. There may be other things going on within the ECU that restore fuel flow and one of those may be what is giving Bugs all the hassle. I don't really know enough more about the Motronic to tell.

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Yes. thumbsup.gif When customers complain about normal operational characteristics of a veh enough, they will try to resolve what ever it is. They will try to make you think your bike is either fixed or replace it. I`ts called a lemon law. You bitch and they get three trys. After that you get a new one. After that when you come back complaining about the new one they will let you know is a normal condition and no fix can be made. Now they have complied with the law and your just a complainer. dopeslap.gif

Mine operates the same way. You need to ride it and enjoy it. Not pick at it. It`s an internal cumbustion eng. That key word is combustion. BOOM Ride it. Let it talk to you and you`ll know its alive like Johnny 5. clap.gifclap.gif

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Yes. thumbsup.gif When customers complain about normal operational characteristics of a veh enough, they will try to resolve what ever it is. They will try to make you think your bike is either fixed or replace it. I`ts called a lemon law. You bitch and they get three trys. After that you get a new one. After that when you come back complaining about the new one they will let you know is a normal condition and no fix can be made. Now they have complied with the law and your just a complainer. dopeslap.gif

Mine operates the same way. You need to ride it and enjoy it. Not pick at it. It`s an internal cumbustion eng. That key word is combustion. BOOM Ride it. Let it talk to you and you`ll know its alive like Johnny 5. clap.gifclap.gif

 

Your logic has a serious hole in it. If BMW genuinely believed that their bike had no issue, and that they simply needed to placate a "complainer," they would have taken the much easier route and refunded my money rather than give me a second bike that would just have me back in their face demanding they fix that one as well. Additionally, if they also didn't believe there was anything wrong with the bike, and that they had thousands that operated the same way, they could have easily let it go to court w/confidence that they would prevail.

 

The second gaping hole in your logic is that the dealer is involved and has absolutely no incentive to lie by claiming they have NEVER seen another BMW with this condition - telling me this was part of the character of the BMW would have been the easiest thing for them to do. BMW is NOT compensating them for a significant portion of the work they did. They are out money on this deal and are throwing in even more $'s to keep a customer. They also had the BMW tech spend several days with them on the job, so there's no chance the dealer is making this up to milk BMW for warranty work.

 

Why is it so hard for you to accept the likelihood that the problem with my bike is not the same thing that you are experiencing with your bike? This is my 9th bike. None of the others I've owned have had this problem... and, YES!!!, they all had internal combustion engines that went "boom," albeit INTERNALLY. I can't count how many of my riding buddies BMW's I've been around that have never had this problem - not even close. The dealer I'm working with has had hundreds of bikes pass through their shop and none of them have had this problem. Don't you think it's much more likely that my bike and your bike are NOT experiencing the same problem?

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Just in case.

I'm not sure about the state you live in, but here in Florida there is no lemon law on motorcycles, boats and other "recreational vehicles".

 

The Lemon Law Does NOT Cover: (Florida)

 

Trucks weighing more than 10,000 pounds gross vehicle weight;

Off-road vehicles;

Vehicles which are purchased for purposes of resale;

Motorcycles and mopeds;

The living facilities of recreation vehicles.

 

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No I did`nt say the injectors are shut down. eek.gif

I said Decel Mode. tongue.gif Yes they can and do reduce fuel on Decel mode. thumbsup.gif

If by "decel" you mean closed throttle deceleration above about 2000 RPM, the system doesn't just "reduce" the fuel supplied to the motor, it shuts it off totally until engine speed drops below about 2000 RPM. This is a standard feature of all Bosch injection system since the L-Jetronic system in the very early '80s.

 

Bob.

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Sorry to tell you this, BMW will never give you your money back..........

And yes the dealer has incentive to do this. It`s called warranty work. Yes they are paid to do it. Your bike has a warranty claim on it or it would not be there for anything to be looked at. Dealers do not work for free.

Don't take this personal. I`m not attacking you. Just trying to let you know how they work it.

Sorry that your having problems but like someone else said.

Don`t be shocked when the new one acts the same.

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I'm amazed that people keep saying TADT, they mostly do have a mild backfire on decelleration but I don't believe for a minute that a dealer and BMW would put all this effort into trying to fix that, it's clearly a different problem. It's hard enough to get BMW to look at genuine problems let alone things they all do.

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The Dealer is making the call.

Until the complaint is addressed by the proper avenues of repair protocol they are acting per BMW guidelines for proper warranty claims. Is the way the law requires.

I`m sure they are looking for the work too.

And as I have said before. Yes it could be something else.

But the indications the owner has explained here, I would think other wise. WE SHALL SEE......... eek.gif

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And yes the dealer has incentive to do this. It`s called warranty work.

 

I specifically said the dealer had no incentive to LIE. The dealer knew that there was always the chance that a BMW tech would show up to verify the problem. Fabricating a problem would put them in a situation of NOT being reimbursed for the warranty claim once the BMW tech showed up to verify the reported problem. In fact, the BMW tech did show up and personally worked on the bike on two different occasions, supplied numerous solutions to test, and authorized several major replacement parts. Does this sound like the behavior of two profit-motivated firms who are working on a problem they believe is "TADT?"

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The Dealer is making the call.

Until the complaint is addressed by the proper avenues of repair protocol they are acting per BMW guidelines for proper warranty claims. Is the way the law requires.

I`m sure they are looking for the work too.

And as I have said before. Yes it could be something else.

But the indications the owner has explained here, I would think other wise. WE SHALL SEE......... eek.gif

 

I have tried through both rounds of this to stay out of this...However:

 

[rant on:]

 

How can you folks tell him he hasn't got a problem if you haven't even heard/seen/ridden/been within a 1000 miles of the damn motorcycle???

 

As much as I love this board and pretty much everyone on it, this has been gnawing on me for a while now!

 

There are some amazing minds here, but we might all learn from this when it finally gets figured out.

 

Let it go and have some faith that he maybe doesn't describe it perfectly enough for you (collectively) to understand the problem, but that there is a problem.

 

 

He promised to get back to this and did. I commend that, and I don't' think we should frustrate/attack someone on the board enough to make him give up on the board at some point, which I'm sure has crossed his mind!

 

[rant off, or at least paused for now]

 

 

Let the rest of us hundreds of interested and apparently, not so smart, folks know how this turns out, if you ever hear back from Germany...

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As previously stated, T.A.D.T., even my CBR XX will grumble on the over run.

 

Glad you are coming to a resolution of the problem. Don't be surprised if the new one doesn't do more of the same.

 

Hmmmm, then BOTH of my R1200GSs musta been broke..

along with my LT,

along with my wife's GT....

 

TATD??? BOLLOCKS!

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How can you folks tell him he hasn't got a problem if you haven't even heard/seen/ridden/been within a 1000 miles of the damn motorcycle???

 

As much as I love this board and pretty much everyone on it, this has been gnawing on me for a while now!

Well I'm inclined to agree with you, and I'm one of the ones who posted a "TADT" reply early on.

 

I suspect what we are talking about here is an matter of degrees. All (or almost all anyway) boxers will occasionally after fire. But this particular one may indeed have a much more severe case of it. At least those who have heard it seem to think so.

 

It will be real interesting if in the end we hear the real cause / answer. Certainly one group or the other is going to feel vindicated!

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ShovelStrokeEd

Steve,

It is a quite common thing on a fuel injected machine. In fact it is pretty much the nature of the beast with a big twin and the Motronic EFI. The 4 cylinder bikes are less likely to produce it to a noticable degree. Think of comparing mouse farts to elephant. Even with a muffler, your gonna notice the elephant. The GS may well have some means, given its throttle bypass controls, to mitigate the problem. Your bikes aren't broken but if you have never experienced afterfiring on any bike, I would be greatly surprised.

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Steve,

...Think of comparing mouse farts to elephant. Even with a muffler, your gonna notice the elephant.

 

Leave it to Ed to explain it in terms even I can understand smile.gif

 

I'm still on track to pick up my '06 elephant this Friday, which likely means Tuesday of next week. I'll be sure report back on whether things still smell... uh, I mean sound funny.

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skinny_tom (aka boney)

[rant on:]

How can you folks tell him he hasn't got a problem if you haven't even heard/seen/ridden/been within a 1000 miles of the damn motorcycle???

As much as I love this board and pretty much everyone on it, this has been gnawing on me for a while now!

There are some amazing minds here, but we might all learn from this when it finally gets figured out.

Let it go and have some faith that he maybe doesn't describe it perfectly enough for you (collectively) to understand the problem, but that there is a problem.

He promised to get back to this and did. I commend that, and I don't' think we should frustrate/attack someone on the board enough to make him give up on the board at some point, which I'm sure has crossed his mind!

[rant off, or at least paused for now]

You sure said it in a lot nicer way than I was going to. thumbsup.gif

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ShovelStrokeEd

Good luck, guy, I really do hope things are resolved to your satisfaction. You have certainly put up with enough to get this far.

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Your bikes aren't broken but if you have never experienced afterfiring on any bike, I would be greatly surprised.

I couldn't agree more. Every BMW I have ever owned has done it to some degree. In fact, my old '85 K100RS was probably the biggest "farter". It also got decient gas mileage and ran to 10,500 RPM (155 to 160 mph) in top gear on the autobahn near Ramstein Germany. The guy I bought it from had tweaked the fuel pump to put out 40 psi and disabled the rev-limiter. Stock is 36 psi.
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Steve,

It is a quite common thing on a fuel injected machine. In fact it is pretty much the nature of the beast with a big twin and the Motronic EFI. The 4 cylinder bikes are less likely to produce it to a noticable degree. Think of comparing mouse farts to elephant. Even with a muffler, your gonna notice the elephant. The GS may well have some means, given its throttle bypass controls, to mitigate the problem. Your bikes aren't broken but if you have never experienced afterfiring on any bike, I would be greatly surprised.

 

...in the spirit of the holidays, which are a gastronomic nightmare, my body's fuel injection system is backfiring so bad right now that shovelstroke would be hardpressed to concoct a remedy.feels like my cat converter has been removed and flowmaster straight pipes are humming. not sure if my octane level is too rich...no doubt that i've got a surging problem and probably will need a spline lube soon as i turn 50 in february. gotta go-holiday snack time! dopeslap.gif

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...in the spirit of the holidays, which are a gastronomic nightmare, my body's fuel injection system is backfiring so bad right now that shovelstroke would be hardpressed to concoct a remedy.feels like my cat converter has been removed and flowmaster straight pipes are humming. not sure if my octane level is too rich...no doubt that i've got a surging problem and probably will need a spline lube soon as i turn 50 in february. gotta go-holiday snack time! dopeslap.gif

grin.gifgrin.gifgrin.gifgrin.gifthumbsup.gifclap.gif

 

Now THAT was funny! thumbsup.gif

 

Jim cool.gif

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Just picked up the new bike/elephant and rode it home... not a creature was stirring, not even a mouse.

 

I even left my ear plugs home to make sure I could detect even mouse-vs-elephant farts... but nothing, nada, zlich, beyond normal exhaust sounds.

 

In addition, I noticed something else that I wasn't expecting. Even though I'm at the beginning of another wear-in period, the thing actually seemed smooth for a big twin. As I've mentioned in other posts I've made on this site, I found my original 12RT to be rougher than my '03 HD. With the replacement version, the HD now assumes its ranking as my roughest running bike.

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Congrats on the new and improved machine. With all that you went through with the bike and then the doubters who fired up their cannons at you, I'm glad it is resolved. Wonder what the official verdict of the problem will be from the factory?

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I've been lurking in the background hoping the resolution would be a happy one.

 

I'm glad you enjoy the '06, hopefully it will meet the expectations you originally had for the '05.

 

Now, if only my CFO would let me trade off the '02....

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