I tried the next test. I didn’t have any wire on hand, so I used a few zip ties hoping to get a few good pulls in before they melted and the TCA went back into position.

This time when I took the car out, I got basically zero boost all the way until redline. Maybe 1psi, just enough to very faintly hear the BOV when I let off.

I was able to repeat this a few times until the zip ties holding the TCA open snapped. After that, it took longer than usual to spool (CCA still open and CRV still plugged), then at the transition, it dropped down to zero psi and held that basically until redline

 

After that test, just for a sanity check, I returned the car back to normal operation, and am now experiencing the same 10-3-5 boost pattern. It’s hard to tell exactly what number the gauge drops to at the transition, it may even be 10-0-5. I can definitely feel a dip in acceleration and then another spooling event up to 5psi.

I will pop the wastegate/precontrol solenoids out and test them again just to double check. I also have some spare actuators for them that I could swap into the car if they are good.

As far as the potential symptom of the secondary turbo being blown, there is no smoke while the car idles, cruises or during heavy acceleration. Also no concerning oil consumption. However, there does seem to be a thin film of oil on the compressor housing of the secondary turbo.

In regards to the wastegate itself, is there a way to inspect the sealing surface without pulling the turbos out? And is that repairable?

Thanks again for all the help, it is greatly appreciated. I’ve learned a lot on the operation of the twins on this car, and I’m very grateful for that

 

You can view the wasegate door, unfortunately you would have to remove the downpipe to see it. The pre control door is the one that's under the plate with the bolts. The only way to repair the wasegate is to replace the turbos. If yours are higher mileage, its possible they are worn out.

You don't by chance have the pre control and wasegate plugs on the solenoids reversed by accident ?

The last couple things that I can think of to test without it pointing to a bad secondary turbo or destroyed wasegate flange is to check the ypipe oring is good and cap the blow off valve as a test.. Its possible the valve is leaking at pressure..... removing the rear turbo air tube and physically checking the blades...... other than that, you've exhausted all the testing. You could retrace your solenoid plumbing and test to make sure before starting to dive into the turbo charger.


~GW

 

Reading through this thread feels like the OP is playing a game of whac-a-mole. That's why I suggested the OP start from zero—pull everything out and remove it all, including the turbos. Ideally, I'd recommend replacing everything with new solenoids and fuel line hardware. We're all learning from this thread, including me, which is a positive. But to the OP, since you're already this far, I would pull and inspect the turbos to see what's going on.

 

Man that sucks hahaha.

On the upside I’ve learned A TON so far, and I’ve inspected and confirmed the functionality of a lot of the components of the turbo control system, so that’s a huge plus. I have some replacement solenoids on the way to replace the faulty ones that I received. Thankfully the car is still drivable and enjoyable, at least compared to how it was running with that huge boost leak.

In the meantime, I’ll do some light inspection like you mentioned. Checking the wastegate and precontrol solenoids again, double checking the harness on them, pulling the intake pipe off of the secondary and inspecting the blades, etc. I have some other maintenance to tend do on the car as well, it needs wheel bearings, pillow *****, various bushings, belts. I’ll probably knock that stuff out and drive the car for a bit and then pull the turbos if there are no other apparent issues or if the findings of my inspection point me to the turbos being the root of my problems.

Thanks again to everyone for the help. I’ll update the thread on my other inspection efforts and then again if/when I get around to pulling the turbos.

 

If you do need turbos, I have a set for sale in excellent condition with no cracks for $500. (I have 4 sets of twin turbos, which is way too many.) If your car still behaves the same after installing the turbos I sent you, I'll accept a return and provide a full refund. After all this troubleshooting, it would be wild if the turbos are the culprit. Keep us updated if you decide to pull the turbos after your inspection and you're left with no choice but to remove them.

To everyone else, could a leaking wastegate flap or precontrol flap cause this issue that he is having?

 

Edit: think I found your problem. Skip to 34:10 in the video. Your symptoms match what he's describing. If the turbo control solenoid on the pressure side gets stuck open, you'll have one run where it transitions into the secondary turbo. After that, it will be stuck in non-sequential mode. I’m assuming this is what you noticed when you first posted about only transitioning once when the car is cold.

 

Are you not completely sure that all the solenoids are working correctly? I was under the impression you had resolved that which is why we moved on to testing the mechanical. IF not, then that needs to be corrected and you need to KNOW that they are all working correctly before preceding.

I'm not totally sure that the turbos are bad. But checking them visually is important.

A huge boost leak like you had can over speed the turbos. Especially if you repeatedly did pulls with it in that condition. The stock turbos don't like that,
and can destroy them in short order.

~ GW

 

Thanks, this is helpful to know. I actually have no idea what the going rate on a set of twins is, but if I learn that I’m in need of them, you will be the first person I’ll contact.

 

These aren’t the symptoms I’m experiencing at the moment. I haven’t seen 10psi on the secondary yet during my testing. Maybe a long time ago in the beginning of my thread when I had something hooked up wrong. I’m half tempted to repeat what I did incorrectly to just see if I can get the secondary to produce 10psi.

But I have performed a “fix” to stop the turbo control solenoid on the pressure side to not stick

 

Here is the current status of my solenoids. I don’t think I mentioned this in detail in the thread, so I apologize if this adds a layer of confusion in the testing.

I ordered brand new solenoids from RHD japan. While those were on their way, I checked every solenoid in my rack. I think earlier in the thread, I highlighted the results of their electromechanical testing with some detail.

When the new solenoids arrived, I tested them as per the testing guide I linked earlier and found all 3 of them to be leaking either vacuum or pressure or both. One person suggested putting a drop of oil in them to see if that improved performance. I tried that, and the performance of 1 of them increased and the problems it was having seemingly went away.

I decided to initiate a replacement of 2/3 of the solenoids, and since that would take a while, meanwhile I decided to swap the solenoids around and put the best performing ones of the lot that I had in the positions that control the twins and conduct other testing until my replacements arrive from RHD Japan. However, I'm thinking I’ll just buy more new ones stateside and save myself the headache of getting replacements from Japan because they are taking forever.

As far as driving around with a boost leak, I actually have no idea how long I was doing that unfortunately. And between times the car was down for testing or other maintenance, I was doing a pull at least once per drive. I will definitely inspect the condition of the turbines and shaft

 

Also bringing up the fact your charge control actuator got stuck open due to the lack of vacuum, this will create a primary boost leak inside the Y-pipe, causing the primary boost to push against the secondary turbo. This results in unnecessary stress on the secondary turbo, which would explain secondary turbo problems.

 

This is true, thanks for pointing that out. I never mentioned this in the thread, but there is a possibility that I broke the nipple on it while removing the vacuum hose. I didn’t think that was relevant at the time. I don’t know if it was already broken or if it was me, but I do remember fighting with the vacuum line a bit, then noticing it was cracked after finally removing the line. Then it just broke off. I want to clarify that I didn’t discover the nipple in a separated condition

 

I just found the final issue and took the car for a drive. I just felt a normal boost pattern for the first time in my entire ownership of the car.

The plugs were swapped on the wastegate and precontrol solenoids.

Thanks again to everyone who helped me diagnose my issues. This has been a huge learning experience for me

 

lol classic, user error and saved by a forum member.

 

There were a multitude of other issues, but yes, that one’s on me

 

You had more than one issue, but you worked through it. That’s what it’s about. A sequential FD is a special experience. Glad you got it sorted out.


~ GW

 

The car feels so much more alive. I really appreciate all your time and effort

 

So does this mean the brand new solenoids that didn't pass initial inspection are working properly or did you find replacements already?

 

That's a good question, I'd like to know too. I heard too many times that new solenoids are bad out the box.

 

I ordered 3 BNIB solenoids. I tried putting a drop of oil in them like you suggested. This improved the performance of one solenoid enough for me to feel comfortable using it. I returned the other 2 solenoids to RHD Japan for replacements. I ended up just swapping the solenoids I had around such that the best performing of the bunch are controlling the twins. I fully anticipate removing the rack again to replace solenoids. Next time the rack comes out, I’m going to replace them all with new ones, provided I receive some that aren’t bad.

 

How did the return with RHDJapan go? I've never had to return anything through them and I've bought a bunch. Their customer service has always been good for me.

 

They basically asked me to send them some sort of proof as to what about the parts were defective. I did my best to take a video of me testing the parts, and explain why they failed the tests. They took quite some time to review the footage, but eventually sent me a return label and said send them back and we'll replace them for free. The customer service was good, but it has been a lengthy process, which is why I decided to just put the car back together with what I had. Still waiting on replacements