Hey all,

This forum has been a huge help to me for the past 8 or so years from my FC vert to now my dream '95 JDM Type-RS. I've been tracking this issue down for the past year or so of ownership and I can't seem to find any solution to my specific problem.

Since owning the car, I have never been able to build more than 3-4psi on the secondary turbo. When giving it full throttle, it'll build 10psi, transition to 8psi at 4500 rpms but then never make it up past 3-4psi to redline. When I let off the gas below the transition point, the BOV makes the classic "psst" sound however, letting of the gas above 4500 gives me a "HOOO" sound. I'll list all of the things I've done to troubleshoot below, but more on the specs of my car. She is 90% bone stock with 96k km (60k ish miles) one owner in Japan and I'm the first owner in the US. It's got an HKS turbo timer, HKS cat back and HKS boost gauge (running off the UIM) and that's it. Car starts great (unless it's been sitting for a while and stumbles until I blip the throttle) and doesn't smoke. Vacuum hovers around 16-17 inHg at idle.

Things I've done to troubleshoot:
-Installed Check Valve in brake booster line to the intake manifold (bought the car knowing that it had a boost leak, heard a pssst sound under the dash, smelled intake air in the cabin and knew that it needed a CV)
-Replaced all Check valves with Viton Check valves
-Used a boost leak smoke tester - no leaks
-Speed of Light's "Sticking Sequential Turbos/ TCA Fix" (Reverted back to stock)
-Replaced Solenoids I/J (Wastegate Control/ Turbo Precontrol) after calling up Atkins' and asking for help
-Pulled the UIM, replaced 80% of vacuum lines with silicone
-Used a Mity Vac to test BOV, Charge Relief Valve, and pressure chamber (all tested fine)
-Followed FD3S.net's "Boost Problem Troubleshooting" thread

The one issue I noticed was that the Turbo Control Actuator arm did not move when going Key On-Key Off. Not sure if this could be the main culprit here but I popped the vacuum lines off and the arm was able to move with a little force. The diagram shows this is controlled by solenoid "E", but I'm stumped since I did the TCA re-route fix to no avail.

Any help from y'all would be great so I can finally pin-point this issue and feel that second turbo!

 

Did you test solenoid f? It was something I considered when tracking down my boost issue. It sounds more like your issue though.

 

I didn't want to risk putting the rest of the rat's nest off to test any of the lower solenoids, so I didn't get to f. The ccv also moves and mine works properly when going key on/off. Did some more digging and came across @boostin13b "Old man's restoration build" and it seems exactly like what his symptoms were when he first got his car.

 

If you haven’t already done so, You might want to test the TCA actuator directly with your mighty vac. And don’t forget there is a vacuum tank as well; the TCA operates using differential pressure and so there’s a solenoid mounted on the ACV to control the vacuum. If you have pressure and vacuum in their respective tanks and you’re not getting TCA movement with KOKO, then you definitely have a problem with those controls somewhere.

 

My second turbo wasn't boosting and I eventually found the c-clip fell off the turbo control actuator.

 

I went ahead and tested my TCA under the car and that tested good. That meant that the only thing left is my Turbo Control Vacuum Solenoid. Was able to get my multimeter on the leads and found resistance to be in the mega ohms. So I pulled my UIM and got the solenoid off the car. Bench tested it with my mityvac on port A, boost gage on port B and 12v to the connector. When I put 25inhg to port A and give it power, I hear the solenoid click but the gage drops ~5inHg. It drops in similar increments each time I apply power. Tested resistance after bumping it and it read 35 ohms. Just wondering if this is a sign it’s clogged and what the normal operation should be.

 

When I purchased my FD, it was totally stock and I did not have a boost gauge. Once the boost gauge was installed I discovered I too did not have any secondary boost. After performing the silicone hose job on the rats nest and testing each solenoid under that UIM, I discovered the stock hoses were rock hard and had to be cut off with a razor blade. After replacing the hoses one at a time, my secondary boost problem was solved.

 

The TCA needs vacuum and boost pressure to move. You can tee into the lines that go down to it and then run your boost gauge to the tee to see if it's getting vacuum on one side and boost on the other.

Once you figure out what it's not getting you can back track and find out if it's a bad boost or vacuum tank, bad solenoid, or loose/misrouted vacuum line.

Also don't forget the charge control valve in the Y-pipe, if that stays closed you're not going to have much boost. They do fail, it's worth hitting that with a Mityvac to see if it holds vacuum.

Dale

 

Thanks Dale,

I’ve tested the CCA before and Ive watched it work with key on and off. With the UIM off again, I’m going to check my rats nest alignment and check solenoid E again. Not sure if my Turbo control vacuum solenoid is working properly though, when I tested it again with port B open, it dumped all the vacuum with one click.