I was getting normal 12-8-12 boost pattern during the cold days. But now I'm again getting 12-6-12psi of boost. What could be a cause for such high pressure drop at transition ?

I tried fiddling with the ProfecB balance dial from 11 o'clock position to 4 o'clock position but it doesnt seem to make a difference.

Is there some check valve I should check or something ?
I get about 3psi of boost in neutral when I rev it (which I think indicates no boost leak).

Thanks !

 

Inspect the check valve on the line from the turbos to the pressure chamber.

 

How do you inspect the check valve ?

Is this the green/white valve you're talking about that can be accessed without removal of UIM ?

 

I'm having this problem as well recently I wouid like to know how to check them as well

 

I also read it could be a faulty Turbo Control Solenoid. To check that one, you need to take off the UIM, right ?

Check valves I think only allowe boost or vacuum to pass in one direction and not the other.

But how to test the solenoids ?

Btw. where to buy MityVac with pressure/vacuum producing capability online ?

 

I just ordered the Mityvac Silverline plus. It's about the only Mityvac that does pressure and vacuum out of the box, and I think it also has higher limits for applied vac. and pres. than the other ones.

I have the basic Mityvac and it works fine, but I needed to get an extra pressure gauge to Tee in when doing pressure, and it's more cumbersome this way. PM me in about a week and I'll let you know how they compare.

It's about $60 from a number of places - ebay.com stores, or google for 'silverline plus'.

Dave

 

I'm also fighting a slow transition and sluggish boost onset. Would a slow CCA be a possible cause?

 

It sounds like you are not prespooling the secondary turbo.

Check the turbo pre-control solenoid. It is one of the pair bolted to the front of the UIM. You should be able to tee a line in there and check for proper operation.

Trace the line to the pre-control actuator on the turbo assembly. Test the actuator with a mighty-vac. Make sure the actuator arm has not come off the lever that controls the gate.

Good luck,

-bill