2002 XC70 Overboost then underboost?

[mbonny]

Hi Guys,

I am still having some trouble ironing out the issues with my recently purchased XC70 (118,000Km).

Symptoms: (diagnosis with a cheap ODBII Bluetooth dongle and Torque app on Android)
Boost appears to spike at 14psi+ for a fraction of a second
Boost then was about 2psi tapering off to 0.5psi then back into vacuum
Performance feels like a non-turbo car

This to me sounded like a faulty TCV, so I replaced the TCV and the yellow and blue hoses with gear from IPD. (Red one looks a bit tricky).

Post TCV Symptoms:
Boost appears to spike at 12+ often, but not always.
Boost then drops to 3psi and seems to stay.
Car is certainly more responsive

Other rare symptoms:
"Reduced Engine Performance" light has come on 3 times in the last 2 weeks under light throttle. Removing foot from the accelerator made the light go out and not re-appear?

My diagnosis:
The old TCV valve was not functioning correctly, some previous mechanic has over tightened the wastegate to compensate, then the TCV has degraded more.

Proposed fix:
Turn the wastegate actuator BACK 3 complete turns and retest.

Unfortunately I cant get the parts required to build a wastegate adjustment tool at a reasonable price. So I am considering the guess and check.

Questions:
1) Do you think that this is a reasonable fix?
2) What boost level should I see?

Thanks in advance.
m

[waffleshill]

5-8psi max. 14PSI is a lot of boost for an XC70. Are you sure the TCV is connected properly? I wouldn't play guess and check with the WG. If you have access to VIDA scan it with it.

[mbonny]

positive that I have connected the TCV correctly.

The spike value could be off as the ODBII reader has a bit of lag in it, so it is not as relaible as a real gague.

I have seen the spike over 20, but I dont think the stock turbo could do that, so I have put it down to a quirk of the reader and app.