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Thread: HELP boost problem

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    HELP boost problem

    HELP 2003 jdm sti, fmic, 3 port boost sol. Usually boosts to 1.4 but will barley go to 1 bar..have removed sol and cleaned its ticking away but not as loud as when i first got it last year. No boost leak as far as i know as its all tight, any idea ??

    I use to hear waste gate flutter coming on boost, nothing now !

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    Full ISDC Club Member Keadeen's Avatar
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    My 2 cents:

    • "all tight" doesn't mean you do not have a boost leak. Could be stone hit your FMIC and punctured a little hole... Not unknown for FMIC pluming to rub on the body and wear a hole... could be split hose etc. Not to mention the vacuum hoses between the BSS/BCV/Actuator/turbo housing can split too and hardly ever able to see that easily. To know for sure each component / section would need to be pressure tested, and all the small 6 or 8 mm vacuum hoses are cheaper and quicker to just replace.
    • Do you have a stock turbo / actuator for the waste gate? If the actuator goes bad(or wg spring) it will not be able to build boost to same levels as before.
    • Try test the 3 port boost solenoid switch (does it seal fully when closed and open fully when current applied).
    • Maybe post the make and model of your 3 port. See if anyone near you with the same BSS and someone is willing to swap out their known good one for yours for a quick test and see if your car then builds boost correctly (that way you know for sure if BSS is to blame, or not, and can order a new one with some certainty... or if same with other known good BSS you can instead go down the more arduous path of leak tests).
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    Pierberg 3 port less than 1k kms on it. Took off the wastegate line and test drove carefully, boosts till 1.4 and i let off so i think its the 3 pprt acting up.

    Oh i bolted it all back together and the 3 pprts started working again and ran as normal, up to 1.4bar... coukd it be a sticky wastegate ? Or sound like a faulty sol ?

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    Full ISDC Club Member BazGF8's Avatar
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    HELP boost problem

    Quote Originally Posted by enda View Post
    Pierberg 3 port less than 1k kms on it. Took off the wastegate line and test drove carefully, boosts till 1.4 and i let off so i think its the 3 pprt acting up.

    Oh i bolted it all back together and the 3 pprts started working again and ran as normal, up to 1.4bar... coukd it be a sticky wastegate ? Or sound like a faulty sol ?
    If your wastegate was sticking closed it would over boost , stuck open would be slow to boost and make some in the higher rpm .

    Run a vac line directly from the compressor outlet to the actuator should boost 0.5-0.7bar

    That will rule out the actuator and point back to the solenoid just change it then it that case , parts fail from time to time.

    The noise you described as “wastegate flutter” is actually compressor surge
    V4 Sti Wagon

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    Quote Originally Posted by BazGF8 View Post
    If your wastegate was sticking closed it would over boost , stuck open would be slow to boost and make some in the higher rpm .

    Run a vac line directly from the compressor outlet to the actuator should boost 0.5-0.7bar

    That will rule out the actuator and point back to the solenoid just change it then it that case , parts fail from time to time.

    The noise you described as “wastegate flutter” is actually compressor surge
    Compressor aurge is that good or bad as it was really apparent after remap till this happened on wot full boost

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    Full ISDC Club Member BazGF8's Avatar
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    Quote Originally Posted by enda View Post
    Compressor aurge is that good or bad as it was really apparent after remap till this happened on wot full boost
    It’s common on them at higher boost levels at low to mid rpm, it’s basically the engine cannot consume the amount of air the turbos providing at that rpm .

    Usually dropping a gear lower will help things
    V4 Sti Wagon

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    Crossed ref my pierberg 3 port and its the same that opel sell so gona get one during the week and hope this issue doesnt come back...

    Does solenoids ever fail ? Or atleast..work intermittently ?

    Anybody got a laptop/obd reader thats works with a jdm sti that would do some logging on thursday or friday ?

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    Quote Originally Posted by enda View Post
    Crossed ref my pierberg 3 port and its the same that opel sell so gona get one during the week
    AP gets tonnes of these from me. I’ll give you a part number tomorrow if it’s the one I’m thinking of.

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    Quote Originally Posted by Sheriff View Post
    AP gets tonnes of these from me. I’ll give you a part number tomorrow if it’s the one I’m thinking of.

    Yeah the Pierberg 7.01024.02.0 on mine is the same label on the vaxhaul/astra part number VXR SRI 55557806

    Also, re wastegate, if it was an issue where it was starting to stick open/closed, would that result in a CEL ? At no point did I get a CEL

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    Quote Originally Posted by enda View Post
    Yeah the Pierberg 7.01024.02.0 on mine is the same label on the vaxhaul/astra part number VXR SRI 55557806

    Also, re wastegate, if it was an issue where it was starting to stick open/closed, would that result in a CEL ? At no point did I get a CEL
    No it wouldn’t as it’s mechanical
    V4 Sti Wagon

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    Not massive knowledge by me but I did a small bit of trouble shooting myself, did you try resetting the ECU?

    If you drive it, and put it into limp mode or what ever you'd call it, put it boosting at actuator pressure anyway, and reset the ECU, if it boosts normally then leaks etc is not the problem.
    It probably will go back to actuator pressure as the problem is still there...

    You tried the green connectors did you? And clean it out?

    Another few things that happened me was the line from manifold to evap thingy wasn't very snug. But that threw a code for MAP. The line from the tee piece to the solenoid has a little joiner in it, which I thought was needed but wasn't, the connector had snapped and was leaking a bit there too. I just replaced with a continuous silicone line. Not sure how the three port works but...

    Try another known working BCS as mentioned above, be a good idea before buying one new.

    Exact same symptoms I've had anyway, intermittent boosting, some days fine and other days half boost (.45bar)
    I replaced the MAF and MAP sensor, both from MattyB in UK.

    It's only happened once since, and I reset the ecu again and been fine since.
    Actually happened on the drive last Sunday, and there was a lot harder driving after I reset it compared to before hand.
    I'll be swapping out the BCS too, just to be sure.

    The new MAF & MAP have made massive difference, before those, ANY TIME I put the foot down through two gears, (whether it be from 1st to 2nd, or 2nd to 3rd) it used boost to .9 and then back to .45, I'd then have to reset the ecu and it would be good then until next time..
    Since I've replaced those, it happened once, over a week ago now. And I have been boosting it...quite a bit😂😂

    As I said, I don't have half the extensive knowledge some of the guys have here, but maybe get your car plugged in and see if MAF or MAP comes up, solenoid otherwise I imagine.

    Also, point to note, afaik, if you reset the ecu and the boost is good, there will be no code history after you reset it, at least there wasn't on mine, so get her plugged when it's not making full boost.

    May be no help to you, may be some, but just said I'd share my experiences..

    Best of luck sorting it man, I know how frustrating it can be

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    Full ISDC Club Member bang's Avatar
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    I've had a similar issue were when in high boost I would lose boost pressure but only in high boost which is 1.3bar.

    I did alot of research which pointed to the boost solenoid, so i followed procedures on cleaning the solenoid and the car drove fine for a bit but kept happening intermittently and each time i cleaned the solenoid and the problem was resolved.

    Part of cleaning the solenoid is to reset the ECU so after it happened again I just decided to try resetting the ECU just to see and it worked.

    But the problem was still not diagnosed untill i did a data log. while driving hard hoping to lose boost i did infact lose the boost pressure and emailed the file to my mapper who came back stating that the ECU was cutting the boost because I was running lean and recomended that I change the fuel pump as it could be faulty and to also check the fuel piping to manifold.

    Like above get a data log done and you should get a diagnosis pretty quick

    Sent from my SM-G920F using Tapatalk

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    did the fuel pump replacement resolve your issue and all sorted now ?
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    Full ISDC Club Member bang's Avatar
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    Quote Originally Posted by SCOOBYCOLM View Post
    did the fuel pump replacement resolve your issue and all sorted now ?
    I haven't got round to that part yet

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    I had a new walboro fitted 1 k ago, better not be that, new bcs on route will fit it reset ecu and work from their. Have checked all hoses etc and no leaks so for

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    So swapped out the bcs with an identical one.

    Not the car hits 1.4bar boost if i drive it on from above 4k in all gears, but as soon as i load the car from sub 3k revs i can feel it pull timing, stutter a bit at 4 k and over boost in all gears ...



    What would the sympthons be off a boost leak ? Or if the wastgate was sticky ? Or the actuator ?

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    And still no CEL or fuel cut

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    Full ISDC Club Member Keadeen's Avatar
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    Quote Originally Posted by enda View Post
    So swapped out the bcs with an identical one.
    Not the car hits 1.4bar boost if i drive it on from above 4k in all gears, but as soon as i load the car from sub 3k revs i can feel it pull timing, stutter a bit at 4 k and over boost in all gears ...
    What would the sympthons be off a boost leak ? Or if the wastgate was sticky ? Or the actuator ?
    So... to clarify... since fitting the new BCS you now see a change...
    - with the old BCS: boost would not go over approx 1 bar (instead of target 1.4 bar)
    - with the new BCS: different behaviour between sub 3k pulll, with slow boost build as it works through the lag window, and then over boosting instead of too low boost. With 4k plus start pulll your boost levels now remain good @ around 1.4bar since fitting the new BCS?

    What are you using to see what boost you are running (separate sensor and gauge, or OEM sensor and reading ECU values)?
    --> would strongly recommend reading boost with separate sensor and gauge (and comparing to what values the ECU is seeing to rule out a faulty reading).

    -->Did you try connecting vacuum directly from turbo housing to the actuator as Baz suggested earlier?
    And... what boost level were you seeing with that?
    And... does it react the same on sub 3k pull vs over 4k before pull start?


    Either way... if now over boosting then not going to be a boost leak as would see less boost - not more.

    Right now, until you can supply a bit more info as per above... could be sensor, actuator or waste gate. If WG pretension rate wrong, or flap catching then could see this behaviour you now described where it overboosts if pulling from sub 3k. A sub 3k pull allows boost to build slower and hence flap can stay closed better and build higher boost... 4k plus before pull brings on boost quicker and hence, if pretension weak, can partially open waste gate flap and let some exhaust escape through the gate and thus reducing max boost.... if this "problem" was already there when mapped then mapping it too higher boost levels would have made the problem worse and hence more noticeable.

    Be careful during testing... during overboost will run lean and can det and do big damage.
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    Quote Originally Posted by Keadeen View Post
    So... to clarify... since fitting the new BCS you now see a change...
    - with the old BCS: boost would not go over approx 1 bar (instead of target 1.4 bar)
    - with the new BCS: different behaviour between sub 3k pulll, with slow boost build as it works through the lag window, and then over boosting instead of too low boost. With 4k plus start pulll your boost levels now remain good @ around 1.4bar since fitting the new BCS?

    What are you using to see what boost you are running (separate sensor and gauge, or OEM sensor and reading ECU values)?
    --> would strongly recommend reading boost with separate sensor and gauge (and comparing to what values the ECU is seeing to rule out a faulty reading).

    -->Did you try connecting vacuum directly from turbo housing to the actuator as Baz suggested earlier?
    And... what boost level were you seeing with that?
    And... does it react the same on sub 3k pull vs over 4k before pull start?


    Either way... if now over boosting then not going to be a boost leak as would see less boost - not more.

    Right now, until you can supply a bit more info as per above... could be sensor, actuator or waste gate. If WG pretension rate wrong, or flap catching then could see this behaviour you now described where it overboosts if pulling from sub 3k. A sub 3k pull allows boost to build slower and hence flap can stay closed better and build higher boost... 4k plus before pull brings on boost quicker and hence, if pretension weak, can partially open waste gate flap and let some exhaust escape through the gate and thus reducing max boost.... if this "problem" was already there when mapped then mapping it too higher boost levels would have made the problem worse and hence more noticeable.

    Be careful during testing... during overboost will run lean and can det and do big damage.

    Im using a prosport boost gauge. I took the vac line off the waste gate , left open and boosted freely in all gears but obviously didnt go much above 1.2/3bar

    I since took the shield off turbo and the actuator arm was moving but i wd40 the actuator and wastegate arm and moved them by hand freely under the spring pressure, easy to move so dont think its stuck at any point.

    Ive been onto aungus and he thinks the wastegate map might need a tweek but im waiting to hear back when he can fit me in, hopefully soon. Seems odd a same brand bcs can vary the map or could have been a case where the bcs was already on its way out when we mapped the car and not its 100% but the map is now wrong

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    Full ISDC Club Member Gary sti's Avatar
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    My advice wait till anghous can fit you in be able to tell for sure what’s up unfortunately a bit of a wait but that’s his field imo
    Super car you have enda

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