St205 Boost Issues Options

[94gt4wrc]

I bought a 94 Gt four wrc. It's has an aftermarket boost gauge and now that's I've owned the car for a while I'm learning and noticing something. I've read that in 1st and 2nd boost is around 8psi and afterwards it's upwards of 13. My car remains at 8.5psi throughout the gears. I checked the codes, only have one error code for wheel speed sensor. And I cleared it and still the same. Could something be wrong with the tvsv? What do you guys think, I'm new to turbo'd cars so any help will be appreciated.

[Nial]

Check error codes again, just because you cleared the code dosent mean it's gone, if the problems causing the code persists then the code will immediately re-appear, in which case the ECU may be restricting your boost levels.

On top of that the boost gauge might be wrong, it might be tapped into a vacuum line that isn't suitable for a boost gauge, it could be another issue such as a weak actuator valve or a leaking vacuum line.

[94gt4wrc]

I've checked the codes a few times and the only remaining one is 42 the wheel speed sensor. I don't think that'd restrict boost. The gauge might be wrong but it would still show the pressure rise after 2nd whether or not it shows the right pressure. How would I look into a weak actuator? The boost still rises to 8 very nice and it always maintains that pressure.

[Jmk91]

I know in my buddy's Cadillac his wheel speed sensor was bad and it did limit his speed. He couldn't go above 90mph until it was fixed. Not sure if it'd affect boost or not but the sensor can't be to much I'd replace it and see if it helps. It can't hurt anything to replace it.

[digs]

Have exactly the same issue. Think it's a weak actuator, a manual boost controller allows me to set boost at 14 psi all the way across, so guessing new actuator at some point!

Mine's actually worse, about 7psi. Thought i had a ct26 first of all, maybe have a ct26 actuator for some bizarre unknown issue!

This post has been edited by digs: Mar 15, 2015 - 5:40 PM

[Nial]

The only way I know to test a weak actuator is to out a known pressure into it from a compressed air line and see at what pressure it opens, IIRC the standard actuator pressure is 0.5 bar which is about 7 or 8 psi, beyond that the VSV valve does its thing, have you checked the VSV valve and the connections too it? Maybe you are running on actuator pressure only? If the VSV valve is broken that would explain the constant 8psi!

[antoine64]

The vsv may have an in and out port. it may only allow air to flow one way. that was what it seemed like when I recently set mine up. the vsv should have 20-28 ohm resistance and should turn on and off when you apply 12v to it. also the air in port is the one on the inside of the vsv. I tried turning it on and blowing through it to test. Make sure the vsv has a good place to dump the air. mine is hooked up to the same air hose and the idle control valve but for testing you could leave it open. it will only blow air not suck it if I am right about the one way thing.

My car has an error 42 and the boost is not affected by it (I think) I was able to boost up to 14psi on my way to work today.

also you might look for boost leaks in your piping if you haven't already done that.