St205 Boost Problem?

April 7, 2006

I've had the ST205 since January, and I have noticed that in normal driving conditions, when accelerating, the boost gauge will register one notch under full. If I bury the pedal, I can get it to go above full, but its a struggle to get it there, ie having to bury the pedal.

The other day I was accelerating as per normal, with the gauge registering as one notch down (pedal 3/4 down), and it suddenly jumped up above full, and gave me a slight VTEC type feeling as the acceleration improved.

What do you think could be causing this 'problem', and what can I check/change to sort it out?

It doesn't seem to make the car that slow, as I can still kill a n/a Celica, but there is obviously something that isn't quite right.

April 7, 2006

I've had the ST205 since January, and I have noticed that in normal driving conditions, when accelerating, the boost gauge will register one notch under full. If I bury the pedal, I can get it to go above full, but its a struggle to get it there, ie having to bury the pedal.
The other day I was accelerating as per normal, with the gauge registering as one notch down (pedal 3/4 down), and it suddenly jumped up above full, and gave me a slight VTEC type feeling as the acceleration improved.
What do you think could be causing this 'problem', and what can I check/change to sort it out?
It doesn't seem to make the car that slow, as I can still kill a n/a Celica, but there is obviously something that isn't quite right.

Lazy Actuator or sticking VSV.... Also check all hoses for boost leaks/crack etc.

April 7, 2006

anything I can direct some WD40 at? lol

April 7, 2006

anything I can direct some WD40 at? lol

Not really the VSV as i'm sure you know is the rather crude standard boost control mechanism, not only is it a right git to get at (back of engine under intake manifold) it's a sealed solenoid valve. Probably best of getting a decent boost gauge and boost controller and ditching the vsv altogether.

As for the actuator it's a sealed unit unfortunately so not much you can do with it. Can check what pressure it opens at by connecting a pump to it and rasing pressure until the wategate rod moves, should start at around 4psi and be fully open by about 9psi.

Also have you checked for error codes, ECU might be holding low boost mode due to an old error code. Dash light goes out when problem stops but ecu still holds the code in its memory and can decide to drop boost.

April 7, 2006

No error codes are showing up.

A boost controller is on the shopping list, but its something that can wait. Wheels are splitters are higher up the list, lol

I shall check all the hoses and filters I can find. I tried to find an inline air filter next to the turbo sensor, but I couldn't see any filter there. I found a small filter coming off either the air filter or dump valve (that area anyway), so I shall give that a clean tomorrow.