I know it's a clichéd thread title, however i've searched through all the "boost issue" threads and they're too broad with description so i don't know if i have the same problem.

Firstly, starting on sat my car would intermittently refuse to boost when accelerating across all gears, when it did boost it would usually boost to 14psi which is what it's set at, but was sometimes hesitant.

Anyway, it was shitting me to tears and it had stopped boosting for a while, so i gave it a boot full in first, it spiked to 16 psi then went kaput and my car wouldn't boost for the whole day and most of today except until around 5.

When i started it up at 5 to drive home from a mates, it started boosting again just randomly, and to the set psi (14), but then it cut out again and then back in, and after that it refused to boost in 1st or 2nd, only in third and fourth.

I also noted that the exhaust note sounded gargly and spluttery as fuck when it wasn't boosting, and there was alot of popping on down shifts (no smoke however).

So i'm pretty stumped, i'm going to book it in to ASG or MMS asap, but any pre-diagnosis would be helpfull.

apologies for the essay

good idea ...

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race tape y pipe running .05 bar till spares turn up.

cheers

Is the car serviced regularly? Could be fouled spark plugs maybe.

Otherwise perhaps airflowmeter.

Any check engine light?

nah no cel,
i get the cel on redline like alot of other people though

and yes it is serviced regularly, how would fouled spark plugs prevent it from boosting though?

and i might add from this morning you can hear a rattling noise through the exhaust when it's cold, so obviously something is coming loose haha

you've definately got fouled plugs. the spluttering of the exhaust is a dead giveaway, as all the unignited fuel that is leaving the exhaust valves is being forced out unwillingly.

essentially, as your RPM increases, the more frequent the spark is needed to match the incoming air/fuel mix. with fouled plugs (which is usually due to excess carbon buildup around the plug itself), this will sabotage the plug's ability to produce a solid ignition source.

check the leads running from the coilpacks to your spark plugs, as one of these might be causing a cylinder to miss. wouldn't hurt to rip out the air flow meter, get some CRC NF Contact Cleaner and give that a clean out either.

But I'm 90% sure it'd be your plugs.

Source some NGK Platinums, get a 5/8" socket, a few uni joints and extenders and you'll be on your way. Not sure how much MMS or ASG charge for a plug swap, but it's roughly an hour-long job - quite fiddly as the chassis rails sit so close to the spark plug recesses in an EJ20.

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03 STi @ 280hp/1.3bar

kk, cheers rstasy

the plugs were due to be replaced soon anyway so it is most likely them.
it's got platinums in there now anyway, wouldn't use anything cheaper.

so i'll have a gander tomorrow and organise something,
thanks again

sorted it, was a couple of loose vacuum hoses.
i went through my car checking for vacuum leaks, and a hose was nearly falling off the end of a pipe.

still going to change the spark plugs though, where's the cheapest place to get a set of NGK iridiums in perth?

I can do PFR6b's for about $75 a set.

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they're platinum's right?

i'd be keen, iridium isn't that much better anyway