2013 gs acceleration stutter - BMW F800 Riders Forum & Registry



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  1. #1
    Nolan6838's Avatar
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    Hey there, I have a '13 f800gs US model that has recently started stuttering and missing under hard acceleration. I cleaned the IAC and it seems to be functioning properly, I changed the O2 sensor, plugs, and will be changing the fuel filter as well. Is there anything else I should look into? I'm wondering if there is any bench test procedure for the fuel rail pressure sensor as that is my next suspect.
    Thanks

    Solved fyi, new fuel pressure sensor.
    Last edited by Nolan6838; 4 Weeks Ago at 06:20 PM.

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  3. #2
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    When were spark plugs last changed and gapped?
    BMW F800ST, 2010, Black, Fuzeblock, Sat Nav, BMW Tank Bag, Givi Touring Screen, Denali Spotlights, Denali CANSmart, Wunderlich Crash Bars, 62K Miles & counting 

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    Do you have access to a GS-911 a motoscan? A scan for fault codes might be helpful.

    I have not tried this my self, but the advice of one of the old experts was/is that if you suspect the fuel pressure sender unit to be bad
    it can be unplugged for diagnostic purposes. The ECU is smart enough to recognize that the sender is not on-line and then
    guesstimate what to do without it, but the ECU may not always detect a situation where it is sending a bad signal.

    It is also possible to bypass the fuel-pressure regulator / FPR (that sits on top of the fuel tank) to see if that makes any difference...
    Blue 2009 F650GS - H-B crash bars, TT luggage rack, Pelican top case, BMW Vario Panniers & bash plate, 20mm handlebar risers, LED voltmeter, Sargent seat, MudSling, a few other trinkets ... I may be just about at the end of the farkle train  

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  6. #4
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    Quote Originally Posted by jrwooden View Post
    Do you have access to a GS-911 a motoscan? A scan for fault codes might be helpful.

    I have not tried this my self, but the advice of one of the old experts was/is that if you suspect the fuel pressure sender unit to be bad
    it can be unplugged for diagnostic purposes. The ECU is smart enough to recognize that the sender is not on-line and then
    guesstimate what to do without it, but the ECU may not always detect a situation where it is sending a bad signal.

    It is also possible to bypass the fuel-pressure regulator / FPR (that sits on top of the fuel tank) to see if that makes any difference...
    I do not have a scan tool. One thing I did try was unplugging the sensor and running it on the stand. It seemed to not make a difference with it plugged in or not. This is why I'm leaning in this direction. I'm mostly looking to see if anyone else has had the same symptoms fixed by a new pressure sensor.

  7. #5
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    Quote Originally Posted by DJ123 View Post
    When were spark plugs last changed and gapped?
    New spark plugs were just installed, no change.

  8. #6
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    I am cheap and lazy so the first thing I would try is to dump in some fuel injector cleaner to see if that makes any difference.
    Richard - Current bikes: 2016 BMW R1200RS, 2018 16.6 kWh Zero S, 2011 Royal Enfield Bullet 500 Classic, 2009 BMW F650GS, 2020 KTM 390 Duke, 2002 Yamaha FZ1 (FZS1000N) and a 1978 Honda Kick 'N Go Senior. 

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  10. #7
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    Quote Originally Posted by Nolan6838 View Post
    New spark plugs were just installed, no change.
    Sorry, i missed that in the original post.

    have you used a different fuel station recently, or a different grade of fuel?

    Is the air filter cleaned and installed correctly? Is the air box secure on the throttle bodies, no air leaks?
    BMW F800ST, 2010, Black, Fuzeblock, Sat Nav, BMW Tank Bag, Givi Touring Screen, Denali Spotlights, Denali CANSmart, Wunderlich Crash Bars, 62K Miles & counting 

  11. #8
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    Quote Originally Posted by DJ123 View Post

    Sorry, i missed that in the original post.

    have you used a different fuel station recently, or a different grade of fuel?

    Is the air filter cleaned and installed correctly? Is the air box secure on the throttle bodies, no air leaks?
    Same fuel grade and usual stations, all air box hoses and filter is in check.

  12. #9
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    when you say hard acceleration, is that in any gear and winding the throttle fully open? or is it at high revs this occurs?
    BMW F800ST, 2010, Black, Fuzeblock, Sat Nav, BMW Tank Bag, Givi Touring Screen, Denali Spotlights, Denali CANSmart, Wunderlich Crash Bars, 62K Miles & counting 

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    Quote Originally Posted by DJ123 View Post
    when you say hard acceleration, is that in any gear and winding the throttle fully open? or is it at high revs this occurs?
    I mean quick acceleration at any rpm, any gear. If I ease into the throttle it usually doesn't happen. Doesn't matter if it's a quick half or full twist.

    Side note; when I pulled the old plugs they were black like it was running rich. I haven't pulled the new ones yet to check what they look like.

  14. #11
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    The fuel rail is always pressurised as the F8 engine has no return/bleed back to the tank. If you were failing on low fuel pressure i would think you'd feel it all across the rev range, regardless of throttle input (i am only assuming here - i have no experience in fuel issues on this bike)

    Have you done a TPS (throttle position sensor) reset?

    1. Turn on ignition but do not start the bike
    2. Turn the twist grip from zero to fully open and hold fully open for 5 seconds
    3. Wait 5 seconds and repeat step 2. another 4 times (do 5 times in total)
    4. Then turn off the ignition and wait at least 15 seconds before turning the ignition back on.
    5. Ride and try
    BMW F800ST, 2010, Black, Fuzeblock, Sat Nav, BMW Tank Bag, Givi Touring Screen, Denali Spotlights, Denali CANSmart, Wunderlich Crash Bars, 62K Miles & counting 

  15. #12
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    Quote Originally Posted by DJ123 View Post
    The fuel rail is always pressurised as the F8 engine has no return/bleed back to the tank. If you were failing on low fuel pressure i would think you'd feel it all across the rev range, regardless of throttle input (i am only assuming here - i have no experience in fuel issues on this bike)

    Have you done a TPS (throttle position sensor) reset?

    1. Turn on ignition but do not start the bike
    2. Turn the twist grip from zero to fully open and hold fully open for 5 seconds
    3. Wait 5 seconds and repeat step 2. another 4 times (do 5 times in total)
    4. Then turn off the ignition and wait at least 15 seconds before turning the ignition back on.
    5. Ride and try
    I haven't found a straight answer yet so correct me if I'm wrong. I've gathered that the fuel pump runs at 2 different speeds based off of demand so if the pressure sensor is failing in that it reads lower than actual, wouldn't the pump try to compensate by running at the higher pressure and possibly causing more fuel to be injected on each injector pulse?

    As far as a tps reset, is there any sort of visual or audio confirmation that it has completed? Ive read about it before and each person's process is slightly different so I don't know which one is technically correct.

  16. #13
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    If the fuel pump does, then even rolling on the throttle and running at higher RPM's i would think you'd have stuttering issues too. If the sensor is faulty it would still reach that point where it is not supplying enough for what is being asked. (i have no experience of this, or in-depth knowledge about the fuel pump.)

    There's no TPS reset confirmation on the F series, as far as i'm aware. But usually you can 'feel' if there is a difference when you next ride it.

    Does it do the same stutter if you rev it when stationary?
    BMW F800ST, 2010, Black, Fuzeblock, Sat Nav, BMW Tank Bag, Givi Touring Screen, Denali Spotlights, Denali CANSmart, Wunderlich Crash Bars, 62K Miles & counting 

  17. #14
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    Yes it stutters on the stand on a quick throttle rip.

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    Have you ran it with the fuel pressure rail disconnected? I think it should run, but may show an EML.
    BMW F800ST, 2010, Black, Fuzeblock, Sat Nav, BMW Tank Bag, Givi Touring Screen, Denali Spotlights, Denali CANSmart, Wunderlich Crash Bars, 62K Miles & counting 

  19. #16
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    Quote Originally Posted by DJ123 View Post
    Have you ran it with the fuel pressure rail disconnected? I think it should run, but may show an EML.
    If you mean the sensor disconnected, yes briefly on the stand. I didn't notice any difference. I bit the bullet today and ordered a new sensor. Turns out it's available through bmw car dealerships as it was also used on some cars. I'll find out Tues if that was it.

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  21. #17
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    There is no test for the fuel pressure sender in the BMW manual. But it infers that a fault code would generally be stored.

    Here's what the Haynes manual has:

    Click image for larger version. 

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    Blue 2009 F650GS - H-B crash bars, TT luggage rack, Pelican top case, BMW Vario Panniers & bash plate, 20mm handlebar risers, LED voltmeter, Sargent seat, MudSling, a few other trinkets ... I may be just about at the end of the farkle train  

  22. #18
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    Solved. New fuel pressure sensor fixed the issue (I hope). Went for a couple rides a day apart and at first it had some slight hesitation but once warmed up it went away. 2nd ride was fault free.

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  24. #19
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    I'm guessing that the initial ride was slightly off due to the "adaptation" values for the engine re-settling.
    Blue 2009 F650GS - H-B crash bars, TT luggage rack, Pelican top case, BMW Vario Panniers & bash plate, 20mm handlebar risers, LED voltmeter, Sargent seat, MudSling, a few other trinkets ... I may be just about at the end of the farkle train  

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