Poor Idle/starting When Hot

Discussion in 'Technical Help' started by Fourbears, Jun 28, 2018.

  1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.
  1. Fourbears

    Fourbears Noble Member

    Dec 8, 2017
    498
    413
    Norfolk
    Having successfully got an MOT on my Sprint ST 955 today it is apparent that it likes to stall and be troublesome starting when hot. Having done a bit of research (Googling) it seems that the likely culprits are the vacuum hoses leaking and/or the IACV sticking. I know the hoses have been replaced on mine as they are silicon (which I will be replacing anyway) but is there anything else that may cause this issue?
     
  2. Rocker

    Rocker Elite Member

    May 1, 2016
    1,662
    800
    Suffolk
  3. Fourbears

    Fourbears Noble Member

    Dec 8, 2017
    498
    413
    Norfolk
    I have used TuneECU and reset the TPS but it still seems the same. From TuneECU the IACV is set at 3 - is that correct?
     
  4. Sprinter

    Sprinter Kinigit

    Aug 17, 2014
    6,026
    1,000
    uk
    If you diconnect.Stsrt bike,no throttle, idle for 12 minutes or until fan kicks in.It resets.
     
  5. Fourbears

    Fourbears Noble Member

    Dec 8, 2017
    498
    413
    Norfolk
    Thanks. So reset TPS then disconnect the cable and let it do its thing?
     
  6. Sprinter

    Sprinter Kinigit

    Aug 17, 2014
    6,026
    1,000
    uk
    No.
    with the bike standing, as normal.nothing connected.
    Without touching throttle.
    Start.
    Leave until fan starts or 12 mins. Thats it.
     
  7. Fourbears

    Fourbears Noble Member

    Dec 8, 2017
    498
    413
    Norfolk
    Ok I did that and it has an uneven idle. Went for a ride of about 20 miles and it will not idle when warmed up. When I got home it would not restart at all although it was starting to fire. I have already replaced the vacuum tubes, cleaned and checked the IACV. So could it be the injectors/fuel rail - after all it has done 112k! I am at a bit of a loss to know what to try next. It will start from cold almost straight away although it takes a second or two of cranking before it catches. Any ideas?
     
  8. Fourbears

    Fourbears Noble Member

    Dec 8, 2017
    498
    413
    Norfolk
    Well I have used it a couple of times and the temp gauge goes up and down. The fan is working but I'm guessing that the radiator should also feel hot when the engine is fully warmed up. Mine doesn't feel hot so I'm thinking it's blocked. Probably by the K seal a previous owner put in it so I need to replace it. Am I right thinking the rad should be hot?
     
  9. Tricky-Dicky

    Tricky-Dicky Crème de la Crème

    Dec 12, 2016
    2,444
    1,000
    Norfolk UK
    A common cause of bad hot start and and idle on most cars is a failed ECU coolant temp sensor, it causes the ECU to run a richer AFR by default so thats worth checking.
     
    • Like Like x 1
Loading...
Similar Threads - Poor Idle starting
  1. Pedro1340
    Replies:
    6
    Views:
    1,051
  2. beerkat
    Replies:
    70
    Views:
    3,817
  3. Iceman
    Replies:
    10
    Views:
    2,344
  4. Brian Pinn
    Replies:
    4
    Views:
    948
  5. Rainman
    Replies:
    16
    Views:
    2,838

Share This Page