yoramw

I am still struggling to get the car back to 100% shape.

After the balance shaft gear and the short circuit problems I faced, now I think I am down to a vacuum leak.

The symptoms where that car idles fine and if I am gentle on the throttle it accelerates fine, but when I floor the gas paddle or get to boost, the car hesitate and does not seem to be running as it should (even without any load).

My suspects where ignition and vacuum.

When I tested vacuum by conducting the cigar test, I see smoke coming from under the intake manifold as you can see if the video:



My wife took the videos while I was blowing smoke into the vacuum line going from the brake booster.

Am I right it is coming from the thermo valve?
Can I bypass the thermo valve and connect the two lines together and go for a drive to ensure this is it or am I taking a risk with the fuel fumes?

Dave951

With everything in place access to the thermo valve is the issue. If there is enough room you could replace the valve with an appropriate bolt, connect the 2 lines together and diagnose. I wouldn't be surprised if one of the plastic nipples is partially broken.

I'm not sure if the thermo is really the route cause of your reported running issue however.

yoramw

I agree that removing the thermo valve s challenging without taking off the intake manifold.

However, if I understand how this thermo valve works, it is close the connection between the two lines up until the engine is warm and then it opens it up,

If this is correct and there is not flow other then between the two lines, I think I can just disconnect the lines from it, keep it there and connect the lines to each other. No vacuum flow should go in or out of the valve even if it is still attached. Is that right?

Vincent C.

it may be that the elbow going on the valve is swollen ....you may change that first.....

yoramw

I connected the two lines going to the thermo valve together (i.e. it is now going directly from the throttle body to the control valve next to the diagnostic port.

The can now revs without hesitation when I floor the throttle up until I get some boost (around 1.2 bars on the gauge). Then it seems to loose momentum and does not give me the power I usually get out of the turbo.
I also feel at that point that the engine isn't as smooth as it is up until this point.

Dave W.

I'd recommend doing a pressurized boost leak test. Typically, a boost leak will cause the car to run too rich when it hits boost, which can cause the engine to misfire, buck or surge. There's also a chance it's running very lean due to a lack of fuel, so check the pump and filter. A lean condition at full throttle will also reduce power and feel similar to an excess rich condition. Have you read the spark plugs? Ideally you should have a wideband O2 gauge to get better data on this problem.

yoramw

I do not have a wide-band gauge, though I am going to oder one.

Any pointers to how to run a boost leak test? is it similar to vacuum leak test?

I will take out the spark plugs and see how they look.

Thanks for the tips

yoramw

Finally car is working as it should :-)

I found two other problems that I fixed:
1. Bypass valve was leaking badly - I replaced it.
2. The hose clamp that holds the silicon piece connecting the hard pipe to the throttle body was a little loose

Car now get to full boost and it is much fun.