2008 hatch sti boost issues.

Discussion in 'Help, Support, Bug reports & Problems' started by jamieliez555, Feb 10, 2017.

  1. jamieliez555

    jamieliez555 New Member

    Hi all,
    Can anyone help I have a 2008 impreza 2.5 sti. The car has been remapped and runs really well BUT every 3/4 days the car loses boost and runs flat. I have replaced the dump valve because I found the piston was sticking (standard). Once boost drops off I found that if I disconnect the battery for approx 1 hr once reconnected boost comes back and runs fine again approx 4 days later boost drops off. Possibly when sat ticking over for 5 minutes or so ??. Please has anyone have any ideas what the problem/cause of this fault could be..
  2. ELV1S

    ELV1S Administrator

    I'm sure someone will be along soon to help you Jamie, maybe one of our sponsors could pop in and help or you could maybe contact them?

    Have you tried the maff sensor?
  3. jamieliez555

    jamieliez555 New Member

    Hi elvis.
    Thanks for your response I think it is something electronic ie. Boost solenoid or maf sensor but if the maf sensor was in fault would it pull up the engine management light on the dash??. Because i regain boost once the battery is removed I wouldn't think it was a boost leak ?
  4. ZANNY


    Does the engine light come on? I wouldn't recommend resetting by taking the batterey off as the car is registering a fault when not boosting as elvis says your best off taking it down to someone who mows what they are doing to prevent further damage as it's going into limp mode for a reason hope you sort it let us know how you get on I can personally vouch for cams down to earth and know what they are doing and won't have your pants down

    Just my 20p's worth
    jamieliez555 likes this.
  5. It probably WON'T put the engine light on - when a MAF's is faulty it starts to under reading the air flow.
    As its still producing a signal the ECU "thinks" its getting good info, hence no light.
    The only way to see if its good or not is to take a live reading via diagnostics, or use a known good one (off another car) to see if that fixes your issue.

    Have you done anything else to the car other than the dump valve - IE Changed any pipes, fitted a boost controller etc ?
    jamieliez555 likes this.
  6. jamieliez555

    jamieliez555 New Member

    The car has a prosport boost gauge fitted and the T-piece was fitted pretty poorly so I had the boost hose replaced and I haven't refitted the T-piece. I found the dump Valve piston was extremely stiff and felt it could of started to seize up. Which has made a vast improvement once replaced. there are no engine managment lights on the dash and no fault codes in the ecu but because the fault can be intermittent I could put money on it that it's running perfect when booked in for diagnostic tests. I will replace the MAF sensor and will see if that clears the fault.
    Many thanks for your response.
  7. When you changed the boost hose did you make sure the restrictor pill was fitted in the new pipe ?

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