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Boost problem ST205
http://www.gt4dc.co.uk/forum/viewtopic.php?f=13&t=5798		 Page 1 of 1
Author:  Scarymo [ Tue Jul 17, 2012 8:46 pm ]
Post subject:  Boost problem ST205
Hy Guys.

I'm just joined your forum and need some help.
Can't find it by searching the forum.

But at first the specs to my 4.
Its a 1996 with 3S-GE cams, 3" Turboback exhaust with Cat, unknown Boost-Controller. Everything else is OEM.

A few days ago i got a problem with boost presure. It was a very hot day and i pushed the pedal to the metal and suddenly breaks the boost pressure from about 16psi down to 9psi and won't go up again. The first DTC was 54, i've fixed this, never came up again.

Have checked many things.
DTC,Tubes, Intake & Exhaust, Waste Gate actuator, Turbo-VSV, Turbocharger, MAP-Sensor, BOV (OEM Toyota)

I've removed the Boost Controller and mounted the wires back to OEM Turbo VSV, then i made a test round with external boost gauge.
Something about 22psi came up on my gauge. oO
At this high pressure one tube going to the BOV was disconnected.
Then i looked to the DTC, 31 was saved. I think the lost tube was the issue for that DTC.

Any ideas?

Long story and bad english, hopefully someone can help me.

Greetings
Author:  Nibbles [ Tue Jul 17, 2012 11:45 pm ]
Post subject: 
Hi and welcome to the club.

If the small vacuum hose has come off the dump valve, it can open as a pressure relief valve and release air to limit boost. The small hose pulls the valve open when throttle is shut, but also holds it closed when the manifold is at boost pressure.

If boost is controlled by ECU (external boost control removed and TVSV connected) then most fault codes will drop boost to about the pressure you have. You should see ECU light and be able to read a code if this happens. If boost is controlled by external controller, then ECu faults will not drop boost.

Can you hear a hissing of air escaping when on boost ?

Another common problem is a split in the hose between turbo and intercooler or the throttle body rubber, often on the bottom so not easy to see.
Author:  Scarymo [ Wed Jul 18, 2012 11:35 am ]
Post subject: 
Hi.
The bigger hose from the bov goes off when i get on boost.
Yes i can hear escaping the air at high boost. I'll have a look at the throttlebody again.
Boost is ECU controlled no CEL came up, no fuel cut.
I'll try another test drive without TurboVSV hose one the waste gate actuator, then the boost should not go above 13psi right?

Greets
Author:  two_OH_five [ Wed Jul 18, 2012 5:33 pm ]
Post subject: 
You will need to block the pipe which runs to the turbo vsv

For testing this could be done with vice grips or something similar

But if you hear air escaping somewhere there is a leak
Author:  Scarymo [ Thu Jul 19, 2012 9:29 pm ]
Post subject: 
Hi.

I block both, outlet from wastegate and the tube to the T-VSV.
Today i bought an Reliefvalve, i'll fit this and try to manage the boost max. to about 17psi.

I've noticed a clearance on the turbine wheel, i'll strip down the turbo and have a look at the wheelshaft, hopefully i can use a rebuild kit. Any advices?
Fensport offers a rebuild kit for the CT20b, what you think about this?
Author:  Sirius [ Thu Jul 19, 2012 9:46 pm ]
Post subject: 
The turbo assembly has to be balanced, I would not want to repair one myself.
Author:  Scarymo [ Thu Jul 19, 2012 10:27 pm ]
Post subject: 
This kit includes no wheelshaft, only 360degree thrust bearings, o-ring, circlips and other stuff. No turbinewheel or compressorwheel.
I thought this would be like changing rod bearings or something like this.
Author:  Scarymo [ Sat Jul 21, 2012 9:19 pm ]
Post subject: 
Today i built-in the Reliefvalve, boost is limited to aprox 17psi.
Throttlebody gastket renewed and cleaned.
When the valve opens the boost varies a little bit, doesn't matter anyway.

At this point my problem has gone, can't tell what the issue was.
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