Well here we go, first post, K1300GT runs poorly, too rich

[Honolulu]

Got on the bike (2010 K1300GT, 30,000 miles) to go home and it ran poorly. Would barely hold idle. Dies if I ease on the throttle but will rev (roughly) if I yank it. Replaced all four coils (at least one was suspect), four very sooty spark plugs and sooty O2 sensor, didn't help anyone but the vendor.

I used the GS-911 to data log, see attached pdf. O2 sensor voltage about 0.9, cat is glowing when I look in the pipe, rev it to see the black smoke. Rich, for sure, but why?

I need to ask more questions before the dealer gets it. One, is the fuel system non-return? If so I assume the fuel pump is controlled directly by the BMS-KP unit. How is fuel pressure monitored? I get a fuel pressure reading from the GS-911 of about 2878. (units unknown). If 2878 millibars that's about 42 psi which sounds about right. Using the live data function, the throttle position sensor seems to be working. I trust the new 02 sensor. The ambient air temp is about 30 degrees lower than actual due to a resistor (forget the brand) on the intake air temp sensor when I tried to cure hot stalling which still happens.

Anyone got a suggestion?

[Honolulu]

I've learned a few things lately from https://www.topspeed.com/motorcycles...64957.html#top and http://www.bayareamotorsport.com/alphan.html

You have to scroll about 1/3 of the way down, and it's written as a review of the K1300S, but I think it's equally applicable to the GT model.

The injection system is alpha-N rather than MAP or MAF based, meaning the primary inputs to the ECU are throttle position (via the throttle position sensor or TPS) and engine rpm (I suppose via the crank sensor). Additional inputs include engine temp, air temp and air pressure. This site http://support.moates.net/theory-alpha-n/ describes alpha-n systems as generally antique given their limitations. But here we are...

Fueling is non-return, controlled by the ECU determining injection volume and timing. I infer the ECU tells the fuel pump how much pressure to put out and that the fuel pump controller, mounted alongside the pump, is a key element. I assume controller modulates pump amperage (and thus fuel pressure) in response to a control signal from the ECU. What then is the function of the fuel pressure regulator on the fuel rail, and does it also communicate with the ECU? The fiche doesn't indicated whether this is only mechanical or an electronic sensor. I think it's the latter. As with other types of injection, the 02 sensor provides feedback to the ECU.

Cold start engine speed controlled by the ECU and the idle air controller at the bottom of the airbox which allows additional air to bypass the throttle valves. The IAC has been known to cause problems.

Thanks, BMW, for a fiche that's so limited in the information it provides, basically only part numbers, application dates and approximate location.. Thanks even more, for nowhere publishing engine operation information beyond basic physical parameters.

The above should point me toward my problem, but I'm not feeling it yet. I believe, based on real-time logging with the GS-911, that the TPS is working, fuel pressure in what should be an acceptable range (about 42 psi at 2700 rpm), barometric pressure appears correctly reported as well as engine temp. What's left. since all sensors seem to be operating? Only that one of these is not in normal range? What then are the normal ranges for each? Nobody seems to know, or say.

[Honolulu]

It seems there is a solution.

The dealer hooked it up and communicated with Hans und Fritz, and all is revealed. Despite the GS-911 returning suspiciously constant fuel pressure readings of about 2700, or 42 psi (which constant pressure was suspicious to me) the actual pressure was MUCH higher, causing overfueling. Apparently the fuel pressure sensor on the fuel rail was kaput. Since replacement requires a lot of "going in there" I told them to make it happen. It'll cost about a grand. Yep, USD$1000. I will review the rep-rom and see just how many FRU's are allowed and maybe there can be some negotiation; the service manager has suggested there's some wiggle room. The part will take 3-5 days to come in and they should install in a day.

[RS530]

So, was that the problem???

[Honolulu]

See above "apparently the fuel pressure sensor on the fuel rail was kaput." I'm unclear exactly how this was determined. I knew the GS-911 reported fuel pressure being constant at about 40 psi from idle to about 3,000 rpm. But no one could tell me whether this was supposed to be so, thus my suspicion could not develop into a repair plan. I couldn't determine whether the fault lay in the ECU, the fuel pressure sensor, the fuel pump relay or the fuel pump.

The dealer tech somehow was able to determine the facts and replaced the pressure sensor. The total cost for repair, including properly seating a coil that I'd left not quite attached, rose to $1400. I can only say that aside from a new battery, changing oil plus filter and a set of tires, this is my first unexpected in the 2.5 years I've had the bike. Averaged out on a cost per year basis it's not too bad, but I hope it doesn't happen again any time soon.

BMW = Break My Wallet

[ZATO]

[aviator]

Thats on of the reasons I let my K1200S go. And the fact that I could not ride it anymore because of my neck.

[ZATO]

I know about that neck thing. You look comfortable on the XR.

[aviator]

Yes, ZATO, I totally fit in on the XR, more so then my GSA.

[EMTNEK]

This is good info now that I have a high mileage GT and a 32K mile GT. Will help if I ever need troubleshooting.