Had a boost problem since I had my engine swapped. The mechanic who did the work for me never worked on this car before (in Italy). I get boost when the engine is cool, but not always 10, most of the time it's 6, but sometimes 10. As it heats up, it lags big time. I got a vaccum tester and T'd into the vac chamber, nothing. Took the extension manafold off and compared what I could see w/ the color vacuum chart on this site. Seems some of my check valves are missing. The vac chamber was hooked to the rat's nest, not via a check valve, to the red dot in the photo. The green dot had a hose, but wasn't connected to anything. Yellow was connected straight to the manafold also. Where does yellow dot belong, the chart is hard to read, but seems to go to the pressure chamber... I took one of the check valves and connected it in between green dot in the photo to the intake. and connected red dot to the vac chamber. What do you think?

 

Well, with the vacuum box hooked up right, I no longer have the lag issue, was getting a full 8ish PSI for 20 min of driving. When I go over 4500 RPM, the boost starts to drop, almost to zero. I figured it would though, what else the mechanic has hooked up all wrong... plus missing check valves here and there, bet he broke them and said nothing. I will continue eventually troubleshooting the second turbo issue, and if at the same time it doesn't fix my 8 lbs of boost instead of 10, then I'll troubleshoot that later. Maybe the pressure side is not right, and it's not pushing the turbo control door all the way closed, we'll see.

 

Those are all possibilities. Good luck.

 

I had similar issues with the check valve on the pressure side put in backwards (no one to blame but myself unfortunately). It will cause boost loss above 4500 rpm (but not always).

Sounds like you are going to have pull the UIM and just go through and check all the hoses and check valves. Good luck with it.

-b

 

Consult this:

 

I have the vac hose diagram... I had the extension manifold off and looking at the rats nest, I'm a bit nervous about taking it off and reconnecting everything, seems like such a crazy maze. Also, the picture is a bit confusing, right around the charge relief solenoid (letter H in the diagram), but the color code helps. Looking under the extension manifold, that area was hard to follow too. I'll just take pictures as I take it off, can't do much more badly than the mechanic did.

 

It is a crazy setup indeed. You need good eyes to stay focused on tracing each path. Although somewhat unrelated to your problem, I have to ask. If your mechanic did a complete hose upgrade, is it possible that the restrictor pills might have been discarded with the old hoses? That normally results in a consistent, low boost of around 7 psi, but the 10 psi that you see may just be intermittent boost spikes.

 

Thank you RD turbo. When he put the new engine in, he did re-do a lot of the hoses. I assumed that he didn't touch those for I've hit 10 PSI on numerous occasions. You say that could be boost spikes, days when I get 10PSI, it hits it quick and holds, but I'd better check to ensure they are still there. Thanks for the idea.

 

If it hits 10psi and holds, it's not the pills. I would suspect a sticking solenoid, leaking check valve, or some other sinister issue.