Ok .. I’ve been trying to track down this annoyance for quite a while.

Here’s the scenario: Primary boost is fine. On transition (4500 RPM) the secondary will hit 10psi then gradually drop off to about 6psi and hold at 6psi until redline.

My boost pattern is: 10-8-10-6

Here are the flow mods to my car:
• HKS Downpipe
• Cheap bastard intake
• I also have a full silicon vacuum job

Here’s what I trouble shot so far:
• Replaced all plastic check valves with OEM ones
• Checked that Pressure and Vacuum tanks hold pres. and vac.
• Hooked MityVac to Charge Control Actuator – Moves fine
• Checked Wastegate and Turbo Precontrol actuators – Moves fine and are adjusted correctly.
• Made sure restrictor pills were in both WG and Precontrol vacuum lines
• Tested both CRV and BOV per FSM – Checked out fine
• Made sure WG Solenoid and Precontrol Solenoid connections are not switched


I’m pretty sure it’s not a boost leak because the primary will hold 10psi all day (please correct me if I’m wrong). I also checked to make sure all clamps were tight.

I’m thinking the culprit is either the WG Control Solenoid or the Turbo Precontrol Solenoid. But I’m not too sure… Any info to further troubleshoot this issue is greatly appreciated!!!

 

I would still double-check for boost leaks. You really should pressure test the system and see if you have any - might be a leak around the CRV that wouldn't show with the 1st turbo. The 90 deg. hose going to the CRV is quite prone to leaking, BTW. Could also be the O-ring where the 2 halves of the Y-pipe join.

Dale

 

Most likely the turbo control system. I would start by checking your main cat.

How many miles on the car/cat?

 

70k on the car and cat. 3k on the rebuilt motor. it's a 93. How would i determin if it's the CAT that's causing the problem? Probably gotta get a new one right?

 

take it off, look at the element and see if it is visibly clogged IIRC.

might be your WG actuator pill being too big also.

 

I had similar problems. My car would run fine for about 3-4 minutes after warm up, then I would get low to no boost on the second turbo.
I replaced the turbo control solenoid and while doing this I noticed that the secondary intake hose has folded in on itself. It has that hershey bar looking platic inside it and I think sometimes it moves around allowing the hose to compress on itself.
So my vote, turbo control solenoid, but also check that intake if you havent already, if its not folded in check for places it might during boost.

 

Ok so here's what I’m going to be troubleshooting next.

• Double check intake hoses and 1” CRV/CCA hoses
• Check CAT if clogged. but I don’t think you can actually look through the damn thing can you?
• Check the Turbo Control Solenoids – There are two of these that I need to check, am I correct? Also, can someone explain what the Turbo Control Actuator does?


Thanks for the input guys!!!

 

i had the same problem 2 weeks ago, i couldnt find it the first time wen i took all my pipings apart off the y pipe, a week later i did it again and finally found the problem, it was a hose that connects to one of the green ***** (iono wat its called) underneath the crossover pipe and that black air chamber, hooked it up and cat tied it and all seems fine now

 

You can check it pretty easily.

unbolt it from the downpipe (assuming you are running a downpipe vs a pre-cat)
get a thin flash light and shine it in there while you peek into the hole.
if it looks like mesh, it is probably ok.
if it looks like a shower drain after shaving your dog, it's clogged.

 

Check for loose Secondary Turbo flange nuts (two 10mm). Also make sure ther CCV (internal butterfly gate) is completely opening at transition.

 

The "loose Secondary Turbo flange nuts" were my problem when I had similar boost patterns. Secondary boost was accompanied by a loud whistle/screaming noise also...