'07 R1200RT "missing" at 5k RPM

[LarryPB]

This one is a stumper. My '07 R1200RT "misses" or "Stumbles" when I open the throttle full and the tach gets at or just below 5k RPM in 6th gear. It'll "miss" or "stumble" until the tach gets to 5250 +/- RPM and then runs to redline fine. It will also do this in 5th and even occaionally in lower gears but mostly in 5th or 6th gear. It doesn't do it all of the time, it's intermittent. You have to be going 70-90 MPH to duplicate though last week it did it in 2nd gear on a slight up grade. BMW tried to duplicate the problem and couldn't. I believe it's way too lean and under certain atmospheric conditions it "misses." If I ride the bike sedately it almost never does it. If I ride it more "sport" than "touring" it does tend to do it. If I roll on the throttle it almost never does it. And when it does do it, if I back off a little, it stops doing it. If I quickly peg the throttle to wide open in either 5th or 6th, when the bike is warm only, it might do it. It scares the hell out of me when I'm passing and need more power. I'd like to solve this problem as this is the best BMW I've ever had. Any ideas?

[dirtrider]

Hi Larry

 

That is a puzzler.

 

A quick guess would be a spark plug acting up or a stick coil starting to get weak.

At light throttle 5K you are probably still on the o2 sensors but as the RPM’s go higher it more than likely goes open loop and therefore richer. Sometimes a little richer can cover up a weak spark or poor combustion.

I have a feeling you are going to need a GS-911 or the dealer computer and even then it might not show anything like a smoking gun.

 

Other than that it is probably parts substitution time until you find the culprit. Maybe try to borrow a couple of primary coils as a quick test. I doubt it is the secondary coils as those phase shift so far at 5K they might as well not even be there.

 

I suppose it could also be something like a fuel pump controller not allowing full pump speed but that is a real long shot. Maybe try temporarily bypassing the FPC to see if that makes a difference. You might also try a top speed run, if it is getting good fuel flow and proper fuel pressure it should run out to about 125-130mph at top speed. If it won’t get to at least 120 you could have fuel flow issues.

 

Have you tried to run it up through the RPM range with a manometer on the TB’s? Another long shot but maybe something in how a throttle cable is tracking in a TB cam such as a small stone or burr.

 

Maybe try running it in open loop for a couple of runs to take the o2 sensors out of the system. That could point to an o2 or fueling issue.

 

That engine also has knock sensors, if one of those is acting up it might remove enough spark from one side to cause a miss or stumble at high RPM medium road load. Again another long shot here.

 

Are you getting any strange noises like a clattering timing chain or spark knock? Are the exhaust pipes the same color where they exit the head? Are the spark plug porcelains about the same color?

 

This is an interesting occurrence so if you find anything definite please post it here so we can learn something from it.

 

[LarryPB]

You're correct in that the dealer computer shows nothing, they say it's perfect. It will go 136 MPH according to my GPS so I don't think it's a fuel supply problem. It does occasionally miss/stumble at 90-95 (around 5-5.25K RPM) or so and then pulls hard until over 125-130 MPH. I will have to check into the plugs but Beemer says that the coils are functioning perfectly. I think I'll replace the plugs to see what will happen. Thanks for giving me your opinion and a new direction to look into.

[dirtrider]

Morning Larry

 

With your top speed running out a bit better than most 1200RT’s it doesn’t seem like you have fuel flow or injector spray problems.

 

Replacing the spark plugs is a good place to start. Or at least swap the lower plugs with the top plugs as the lowers don’t do much at high RPM anyways.

 

I just have to ask? Is your bike only acting up when in traffic or does it do it when you are out by yourself also? My last 1200RT would buffet pretty good at 90-100 mph off the vortices of vehicles way out in front of me. Almost like hitting waves of water in a boat.

 

[LarryPB]

My bike is very stable at all speeds. Yes, I was surprised that it goes as fast as it does. If it would only stop "missing" the way it has been I'd be the most happy guy in the world. I have been suspecting the spark plugs for a while myself. I'll change them immediately, after I get it back from Beemer for the brake recall. Thanks for the comment.

[BeemerLover]

Larry.

 

In my experience, especially with carbureted engines, hard throttle on can create real problems if the system can't instantly provide the proper air/fuel ratio. That being said, the ignition system also needs to adjust and weak parts in that system may be the culprit in your case. I hope checking your spark plugs will solve the problem, but, as you suspected in your original post, you may be dealing with the air/fuel mix.

 

In a computerized system what happens at a hard throttle on depends on what the computer "thinks" is happening vs what is really happening.

 

It could be that a sensor or combination of sensors are not reacting properly in that particular situation which makes the computer call for instant too rich or lean conditions until it gets the proper data. It might be a software glitch which might go away by re-installing or upgrading the software. It could be some restriction on a mechanical sensor (or controller) at some particular point in its range - maybe due to defect, dirt or crud. It could be a non-mechanical sensor that is not giving a proper reading only at some critical point in its range. Because they are but slightly defective, they may not throw any codes.

 

I have an '07RT and will be very interested in how your problem is solved!!

 

 

 

 

 

 

 

 

[NewBlue]

There is a TSB regarding a surge or flat spot when coming off a cruise condition. I beleive it was listed has happening at a speed around 70 - 75 mph then accelerating. Depending on the grear this should put you around 4500 rpm's

The correction, I believe, was a software update.

 

Your dealer should be able to look it up and see if it fits your issue.

 

A fault with the DI ignition system or plugs usually shows up under load, any gear, any rpm.

Short shift the bike and accelerate hard, if it's ignition that's when you should notice it, also watch the tach. Ignition faults can give sharp tach needle fluctuations, fuel conditions will give smoother tach needle movement.

[Les57]

I had a similar problem on my 06 RT at full throttle. It took me a awhile to trace the problem to a loose connection at the stick coil.

 

 

[10ovr]

I have had 3 bikes with the same problem in the shop,,2 GS's and 1 RT,,All 3 were a broken or cracked pin in the connector plug to the coil,,,All 3 guys admitted to pulling the coil with out undoing the wire first,,,It don't take much to crack them,,Just something to look for,,BMW sells a kit to repair them,,, http://i650.photobucket.com/albums/uu227/10ovr/IMG_0034-1.jpg[/img]]

[bobbybob]

If 10ovr's theory doesn't help, I wonder if the fuel injection mapping could be partly corrupted in the computer. Maybe re-loading the ZFE firmware/software....

[LarryPB]

I found it! Took a wild guess and had Beemer replace the plugs. They found that the right cylinder upper plug was cracked! Thanks for all of the advice, I read it all and made the correct guess from what you all said. Thanks for the help. BTW, I had Beemer change the plugs while doing the brake recall and even though out of warranty they gave me the labor gratus! Cool!

[bobbybob]

Glad that worked out so well. Still kinda strange that the missing was at a certain rpm but went away as the rpms increased past that point. Usually gets worse as rpms increase, but maybe the timing changes at that point and was masking it...

[dirtrider]

Afternoon Bob

 

If you look at the 1200 BMW boxer dyno data there is lean spot right about where his problem was. It is just coming off the 02 sensor control in that RPM/load range. A lean spot in the fueling would require more spark KV to ignite.

There is also a phase shift in the 1200 secondary spark plug firing spark advance curve, I’m not sure where it is at 5K but by then the spark on the secondary has shifted considerably from where it is in relation to the primaries at lower RPM’s so at that RPM the secondary’s are pretty well a non contributor to combustion ignition.