STI v3: overboost and fuel cut
 

Hi all,

I've had the engine of my STI v3 replaced (by a second hand one), as the previous one had a bottom end knock, and stood still for half a year.

I've ran into a few issues, but I experienced a while for the engine change).

It seems to overboost and run into the fuel cut. Today, I've installed a boost gauge to verify.

Yesterday it blew off a pipe of the intercooler. I've but it back a few times, but it popped off as soon as it started to make some boost. Today, I've cleaned the pipes and silicone connector, and used some hairspray before fitting, and made sure the clamps were tight.
After warming her up and driving around for a while, it seems to hold. Also, the car didn't overboost and cut out (it goes to ~17 psi, and falls (very quickly, nearly instantly) back to ~14 psi.
However, after 5-10 pulls and driving for another half hour, it started cutting out again. With the boost gauge now installed, I could confirm my suspicions: It goes over 20 psi and then cuts out. Seems to work out with the factory fuel cut at 22 psi.

The car also idled quite low on the beginning of the ride (~500 rpm or so, thought it would stall, but it didn't). It didn't do that yesterday.

The intercooler hose seems to be holding. Could a loose hose cause this problem? What else could it be?
Are the boost levels (17 psi, falling back to 14 nearly instantly) normal? The car seemed fine then.

It has an open exhaust, apexi air filter, fmic, unknown wastegate and unknown fuel pressure regulator, all installed by (one of) the previous owner(s).
A few pictures of the engine bay/unknown parts(if someone knows something about them, please say so! :D):
Edit: threw an error today (see post 9):
Error code 24, found this online:
24 Idle Control System Malfunction
24 ISC Valve (Stick)
24 Open/Short in ISC Valve Circuit

Has it been mapped ? Not surprised its overboosting if it has those mods and hasn't been mapped.

I have no idea to be honest. Bought the car last year, went fine on my way home (500+ mile drive), started acting weird 10 miles before I got home. O2 sensor error was thrown. Noticed that a silicone hose was ripped, replaced that and it went fine again for a while. The O2 error code came up some time later, and iirc, it also cut out a few times on boost. It was 'sorted' by resetting the ECU.
Not long after, the engine went (although it was revved way too hard by a potential buyer on a cold engine, which might have been the cause).

If mapping would be the issue, why didn't it overboost all the time? Especially today. I've tested in 3th, 4th and 5th gear, so that the load was definitely high enough to cause overboosting, but it didn't, so I don't think that's the issue. I have a wideband laying around, I'm planning to get that fitted to see what my afr is.

as the chap above said if i aint mapped it aint gonna work v3 ecu cant be mapped as far as i'm aware you need the apexi or simtek ecu as a direct replacement the air filter and maf sensor dont look happy where they are either hopr that helps ya pal

V3 ecu can have an esl board added and then mapped. See Simon Roe aka jolly green monster or speak to Andy Stevens.

If its boosting too high then try a manual boost controller. That's assuming fueling and ignition is still ok.

Mapping would be a whole other problem, as I am in Belgium :D

But, as said before: if that was a problem, wouldn't I have experienced this problem all the time? As said before, after fixing the intercooler hose, I drove the car very gently for 20-30 minutes (not taking chances with this new engine and new clutch), and did a few runs afterwards, max boost 17 psi, drops to 14 and seems to stay there, without any weirdness etc. Those seem to be the stock numbers, as far as I can find online.

Genuine question, not trying to ignore the advice :)

Mapped a few cars meeting them at the port of Dover from Belguim.

Engine load, turbo temperature and air temperature will effect boost level, also there is a time over the boost level before it cuts so if it peaks just over it may not cut.

I presume its decatted and has a front mount intercooler and induction?

Alternative to having it mapped is to refit a cat and the tmic and standard air box.

Hi JGM,

Still doubt it needs a remap. Did test this on the same day, 2 different effects within 30-60 minutes. Drove for quite a while before stretching its legs, and tested in multiple gears (apart from 1st and 2nd, as the clutch is still running in) on the same stretch of road.
As soon as it went 'bad', it goes quickly to the 20+ psi (20 is the last number on the gauge, 22 psi seems to be right). When it works properly, it doesn't come even close (17 psi and dropping to 14 quickly).

I've had an mx-5 turbo that had boost creep after decatting, it's not like that (it would go quickly to the set pressure, but would slowly get higher because the wastegate couldn't handle it. Now it just goes (seemingly, won't differ much) as fast to 22psi as it normally would go to 17)

I still have my doubts about that silicone connector I refitted. Could that cause these problems?

Just for my information: what sort of money would I be looking at to get a daughterbord or something so the car can be remapped, and how much would mapping be?
It's indeed induction,exhaust and fmic (and FPR and BOV).
It feels quite a bit faster before it cuts out, might consider it after all!

Sorry for bumping this, but the car just threw an error code on my way home from a friend. Car stood still for a few hours, drove it for a mile or 2 and it popped and banged a few times, coasting in 5th gear, between 2-2.5k rpm. CEL flashed for a few seconds and it dropped very low in revs on idling.

Error code 24, found this online:
24 Idle Control System Malfunction
24 ISC Valve (Stick)
24 Open/Short in ISC Valve Circuit