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 Post subject: St205 boost problem
PostPosted: Mon Jul 24, 2017 9:44 pm 
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Clubman

Joined: Sat Apr 29, 2017 8:54 am
Posts: 77
Car Model: None
hi guys
Ok I have a problem
I was cleaning the 205 yesterday and I have fitted new silicone pipes on the inlet manifold
and also the turbo actuator anyway I picked up a bit of silicon tube a put about 5 bar of compressed air into it no realising it was connected to the wastegate actuator (don't ask)
anyway it jammed up and a small tug released it back
too it out later and in now has a bad flat spot in first and second and when it does this its almost like a misfire once its warm it drives perfect when cold the same but its when its been run and allowed to cool for half hour it develops this holding back what have I broken, im thinking the vsv could be damaged as the actuator sends air off to the vsv
I have noticed that when it happens the stock boost gauge stops a the bottom although the turbo is spooling up and if you hit the accelerator it drives through it .
Help advice or any pointers please guys
kind regards Baz


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 Post subject: Re: St205 boost problem
PostPosted: Tue Jul 25, 2017 5:07 pm 
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Joined: Wed Jul 13, 2005 5:10 pm
Posts: 1952
Location: Sunny Fareham, UK
Car Model: ST205
Hi Baz - pressure hose should be fitted to pressure areas - wastegate, fuel pressure regulator and MAP sensor are a must.

Which hose received the over pressure?

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 Post subject: Re: St205 boost problem
PostPosted: Tue Jul 25, 2017 9:00 pm 
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Joined: Sat Apr 29, 2017 8:54 am
Posts: 77
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Hi Kris the hose that comes from the turbo to the actuator

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 Post subject: Re: St205 boost problem
PostPosted: Tue Jul 25, 2017 10:51 pm 
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Joined: Sat Sep 02, 2006 3:13 pm
Posts: 3580
Location: Bournemouth
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Over pressure down the hose to wastegate actuator would only reach the actuator and the TVSV valve - assuming boost is still controlled by the ECU. It's not uncommon to have an aftermarket boost controller fitted which will have it's own valve normally between turbo and actuator, then the second pipe from actuator to the standard VSV is normally blocked off.

If the wastegate jammed open, it's quite likely you have an aftermarket downpipe and the wastegate is jamming on it - not uncommon with many aftermarket pipes.

Is the boost gauge 'staying at the bottom' meaning right at the bottom (negative pressure) or at zero (where the gauge sits with ignition on and engine stopped) - this is important as staying negative would indicate a sensing problem rather than an actual loss of boost.

On a 205, the fuelling is set from manifold pressure so the sensing is critical - and the boost gauge is fed from the same sensor as the ECU uses. The pipe to the sensor (purple coloured, mounted on bulkhead) should come from the 'orrifice' fitting in the middle of the inlet manifold by the throttle body, and should not have any other pipes attached on this path. Any leaks / other sensors attached on this line can affect fuelling.

Another line to check is the small vac. line from the top of the fuel pressure regulator (on end of fuel rail) to the inlet manifold. This sets fuel pressure relative to manifold pressure to keep a constant pressure across the injectors. Without this, it will go rich on idle and weak on boost.

The final check is the small vac. line from inlet manifold to the dump valve. This holds the valve shut on boost as well as pulling it open when the throttle is released.

To describe symptoms of wastegate stuck open - you still get boost, in fact near full boost at highest RPM, but boost is much lower than it should be at lower RPM and especially at the 3000RPM mark where it's only just making good boost with the wastegate shut.

The other thing to be aware of, the ECU deliberately inhibts boost above basic actuator boost when cold. This is to protect the engine from owners with no mechanical sympathy.

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 Post subject: Re: St205 boost problem
PostPosted: Tue Jul 25, 2017 11:23 pm 
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Clubman

Joined: Sat Apr 29, 2017 8:54 am
Posts: 77
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Hi nibbles
Thanks for this the boost gauge was staying at the bottom and only came up under full boost however I may have Sussed it now, as I zip tied all the hoses at the ends and I've not been able to recreate the issue so looks as it may have been a leaking pipe to the map sensor.
Yeah I worked out it would only hit the actuator and the vsv and I was going to remove the vsv from the system as a next move but it does seem sorted out at the moment
I've had this 205 for 22 years and it still throws me under the bus at times. Thanks guys much appreciated
Baz

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 Post subject: Re: St205 boost problem
PostPosted: Wed Jul 26, 2017 3:48 pm 
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Joined: Sat Apr 29, 2017 8:54 am
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Nibbles you say that any other line into the map sensor can affect fueling, I have my blitz boost gauge and turbo timer plumbed into this line and have done since about 2002 could this itself cause issues
Also if the ecu limits the boost in first and second gear via the vsv the Toyota manual gives a turbo test instruction which says "in second gear at 4000rpm open the throttle wide open and measure the turbo pressure" it then gives the min and max value you should get, how does this work if it's limited via the vsv?
Best regards Baz


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 Post subject: Re: St205 boost problem
PostPosted: Wed Jul 26, 2017 11:17 pm 
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Joined: Sat Sep 02, 2006 3:13 pm
Posts: 3580
Location: Bournemouth
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Provided there are no leaks, adding boost gauges etc. in the map sensor line will only affect the reading during pressure changes due to the increased volume in the pipes and the effect will be minor. A slight leak will affect the reading all the time, especially as this pipe is fed via a damping orrifice. It is generally good practice not to T into this line for these reasons, better to T into one of the other lines which has no restriction and no consequences in the event of a leak.

From memory, only first gear has reduced boost on a 205, and first and second gear on a 185. In all gears boost is restricted when cold. It is a distant memory since I ran a standard ECU, although I've just bought a standard 205 so will have my memory refreshed over the coming weeks.

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 Post subject: Re: St205 boost problem
PostPosted: Thu Jul 27, 2017 9:13 am 
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Joined: Sat Apr 29, 2017 8:54 am
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Car Model: None
Thanks nibbles you information is very helpful and much appreciated
Thanks and best regards Baz

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 Post subject: Re: St205 boost problem
PostPosted: Fri Jul 28, 2017 10:02 am 
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Clubman

Joined: Sat Apr 29, 2017 8:54 am
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Just as a matter of interest where could I put the boost gauge line instead if I remember correctly the blitz dual timer instructed it to be put into this line, is there another line that I can use

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 Post subject: Re: St205 boost problem
PostPosted: Fri Jul 28, 2017 7:58 pm 
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Joined: Sat Sep 02, 2006 3:13 pm
Posts: 3580
Location: Bournemouth
Car Model: None
Any of the vac. lines from the manifold.

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 Post subject: Re: St205 boost problem
PostPosted: Fri Aug 25, 2017 9:05 am 
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Joined: Sat Apr 29, 2017 8:54 am
Posts: 77
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Solved :the lambda sensor was the fault


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