Uncontrollable Boost Level! Please Help!

[4G63dsmpwr]

Well I recently bought a 1990 TSi AWD, and I started replacing some things right away. One of the problems I'm currently having is that the boost level will not stop at a certain point.

I've had a few cars like this before, and this one came with an XS manual boost controller. After discovering this problem (the boost guage reading) I bought the right alan key, and turned it down all the way according to the directions - with no result. I removed the entire boost controller, and reverted the car back to stock today.

Its gotten a bit better but around 6k, it still is making almost 20lbs of boost (and running extremely lean I imagine) since I have the stock fuel system.

I looked around the engine bay - all vacuum lines seem to be connected properly. My next thought was the wastegate. Thought I'd post here, and see if anyone could help first. Thanks for the space!

 

[GSXanimal]

wastegate or actuator.

 

[4G63dsmpwr]

Thank you very much for your response.

How do I determine weather it is the wastegate or the actuator? I'm not sure if this helps any, but there was a manual boost controller on the car previously.

I removed it, trying to narrow down this problem of uncontrollable boost. Before removing the controller, I tried adjusting the allen key, and either fully open, or fully closed - there was absolutely no change in the boost. Then, when I removed the entire boost controller - the boost was exactly the same (builds up to 15lbs steady, and will keep going until you let off the throttle)

Thanks again for everyone's help. I have read up, and they say you can test the actuator with an air compressor - I don't have access to this tool however.

Any information/suggestions would be helpful!

 

[96TSi_Chris]

If it is a spring loaded boost controller, sometimes the spring itself will get stuck in a down postion causing a wide open boost surge. Try taking a look at the BC and see if you can put the spring back in a normal position and try the allen key method from there.

 

[4G63dsmpwr]

Thank you very much for your time..

I have heard of the problem you are describing, but I thought it wouldn't be that because of the fact when I removed the boost controller from the car completely, the problem was still there.

Well, thanks again - I will take a look at the boost controller, just to double check and make sure its not busted.

Thanks again, and anyone else's input would be appreciated.

 

[92 AWD ECLIPSE]

Look at the rod on the wastegate actuator and it connects to a pin that open a closes the wastegate valve. You should be able to pull of the Actuator by the two bolts attatching it to the turbo. When it is off move it left to right to see if the valve is working. If the valve is stuck from carbon deposits or what ever, this may be your problem. Just a thought, hope this helps.

 

[4G63dsmpwr]

Thanks very much for your help.

I think the culprit is the wastegate actuator - its looks very rusty and corroded. I can't really do any work on the car, as there is a few inches of snow here.

When the weather improves I'm going to take out the actuator, and try to pull it, correct? And about how much force does it usually require for the spring to compress?

Does anyone have any suggestions where I can buy a used actuator? I don't really want to go through Mitsu for a new one - I think they'll charge me up pretty bad.

Thanks alot everyone!

 

[Enigma_Man]

The way to exactly diagnose what is wrong is:

Disconnect the boost controller. Connect the input hose to it directly to the wastegate actuator. This should stop boost at around 10 psi or so.

If it doesn't stop it, then your wastegate isn't functioning correctly. Either it's corroded, the actuator arm is disconnected / maladjusted, or it's just plain broken.

If your boost _is_ controllable after you do that, then your boost controller needs to be adjusted correctly / fixed.

-Jesse

 

[4G63dsmpwr]

Thanks for the help very much everyone.

I removed the boost controller previously, and that didn't change the problem at all - still exactly the same.

The other day, I grabbed a pair of pliers, and gave a real good tug on the actuator arm. The actuator arm (where it bolts up the wastegate itself, held with a cotter pin) was a bit stuck and rusted.

If I tug on it, the wastegate does move. Doesn't require too much force using one hand and a pair of pliers, does this sound like the spring is operating properly?

Now here is the part that confuses me: After giving the actuator arm a good tug THERE WAS AN IMPROVEMENT. In 1st and 2nd gear, the boost doesn't fly up there as fast, but still will boost up to 20lbs if you let it.

In the higher gears, forget it - if I keep the throttle down for more than a few seconds, I will be pushing 20+lbs of boost

Does this help anyone clarify exactly what the problem is? THANKS AGAIN for all the help!

 

[92 AWD ECLIPSE]

My problem was similar but had the opposite effect. My actuator arm was pushing on the pin so that the wastegate was open just slightly, so that I could not build more than 10 psi of boost. Try taking off the actuator completely and look at the play the wastegate has. Also check that the rod is proper length when the wastegate is closed by putting the mounting tabs of the actuator up against the turbo, and see if the pin lines up when the wastegate is closed. For me I had to close the wastegate so I put washers in between the turbo and mounting tabs of the actuator and that solved my problem. Hope this helps.