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Discussion Starter #1
BIT OF HELP NEEDED,CAR HAS DEVELOPED A MISFIRE WHEN BOOST IS TURNED UP,STARTS AND RUNS FINE NO PROBLEM ON STANDARD BOOST AND WILL ACCELERATE NO PROBLEM AS LONG AS BOOST IS NOT INCREASED,BOOST CONTROLLER IS A SPEC S BLITZ AND APPEARS TO BE WORKING OK,WITH CONTROLLER ON 0 SET AS SAID THE CAR WILL RUN FINE BUT AS YOU TRY TOM INCREASE BOOST WILL START TO SPLUTTER QUITE BED AND GETS WORSE THE MORE THE BOOST IS INCREASED,MAX IS SET @.85 ,BUT IT STARTS TO PLAY UP WAY BEFORE THAT,DID HAVE AN AFM ISSUE A WHILE BACK AND SEEMS TO BE LIKE IT SINCE CHANGING IT,BUT HAVING SAID THAT THE CAR WAS TINKERED WITH BY TUNING CO IN PLYMOUTH BECAUSE OF ROUGH IDLING BY PREVIOUS OWNER WHICH TURNED OUT TO BE THE AFM WHICH FAILED SOON AFTER I PURCHASED THE CAR,AND SINCE FITTING HAS SORTED THE IDLING ISSUE,ANY IDEAS WOULD BE MUCH APPRECIATED,
 

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Fit some new plugs and gap them to 0.8mm if that doesn't cure it then it could be coil pack/s.
 

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Discussion Starter #3
changed plugs and its exactly the same,would it not play up with low boost if the coils were breaking down?
 

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Discussion Starter #5
Not sure to be honest hence the post,cant understand why it will run fine on lower boost though ?
 

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Wont be the MAF if it runs OK off boost, what plugs are you using? coil packs will normally show up lower down but first signs can be limited to boost as the spark is under more pressure during boost.
 

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Discussion Starter #7
ngk platinum plugs,but had the exact same problem before plug change,so tending to move away from that,sounds like something is limiting but on a rapid missfire?
 

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Discussion Starter #9
already had the platinums so just fitted them,same prob as before plug change though but was fine before maf problem or not quite as bad?
 

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Discussion Starter #11 (Edited)
But why only at higher boost?Sorry to sound a bit negative but why will it run fine and accelerate flat out without a murmer on low boost but start to splutter and get worse the more the boost is increased,its not an occasional or random mis either more like a rapid bbrrrrrrppppp lol bear with me cause its doing my nut in
 

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Discussion Starter #14
Do you know what youre actual boostpressure is ? stock ECU ?
not acurately no but the stock gauge used to go to around 3/4 way up fine but now wont run at that level or at least starts playing up well before that,the boost gauge is set at 3 levels i think its 0.4 0.6 and 0.8 but did have spiking issues previously where it would reach 1.0 bar ,and yes its a stock ecu.
 

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Can you somehow verify if youre boost gauge is working properly? (they are apparantly not the most accurate but still)
I'm thinking youre boost sensor might have an issue and tricks the ecu into "over boost" protection??
 

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Discussion Starter #19 (Edited)
had pink label on and replaced with pink label or are there different options?
i know what you mean about overboosting but ran fine before,i never cane the thing anyway and its not really an issue cause its still driveable just more of an annoyance
 

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^ "ran fine before" - before a change of any part or ?

The thought was youre stock boost sensor is messing with you hence the ecu receives a faulty signal of a too high boost level which is not really there.
 
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