TPS and or O2 sensor issue ??

Discussion in 'Crazy-Awesome almost Dakar racers (950/990cc)' started by stormdog, Oct 3, 2013.

  1. stormdog

    stormdog Been here awhile

    Joined:
    Feb 19, 2006
    Oddometer:
    586
    Location:
    Almost Southern Oregon
    I have been chasing a problem on my 2010 990. The short story is, It will barely run at very low throttle openings. But runs great at anything above 1/8 opening. the only code it showed was a defective O2 sensor. I replaced that and ran a test to make sure the wires where not broken.
    I have set the TPS to .65V cold .59 hot. Plugged in to tunecu I am getting a reading of .865 to .924 volts on the rear O2 sensor. The front sensor ( the one I replaced) is all over the place. Cold they both read about .490 When I start the bike it will run smoothly at idle after 30 seconds or so the idlle will get progresivly worse and the volts on the front will drop to near 0 volts. The rear stays around .9 plus or minus. The bike will then fart and pop and then after 10 to 15 seconds will jump back to a smooth idle and the volts will come back up . Then the process is repeated
    So I guess my question is
    Do I have a bad TPS or am I missing something else.
    And how would a bad TPS only affect the one cylinder
    #1
  2. Hipster

    Hipster Long timer

    Joined:
    Aug 31, 2004
    Oddometer:
    2,036
    Location:
    Mpls, Mn.
    Stormdog, my '08 990 runs the opposite of yours. On cold start up it sometimes will stumble and die occasionally throwing error code 18. I replaced the front Lamba sensor and the same thing still happens on cold start up. After about two minutes of warm up time the bike runs great.

    Its seems like my cold start up stumble got worse after I adjusted the TPS from the factory setting of 0.65 hot down to 0.60 hot. I might try setting it back closer to 0.65 to see if my cold start up improves.

    It's possible you could have a bad TPS sensor, a few riders have had sensors go bad. Do a search to see if your symptoms are the same as theirs.
    #2