I'm not saying it's a bad idea to have new solenoids... BUT you could replace all the solenoids and still have a problem. Without diagnosing the problem you are just throwing parts at it and this system has A LOT of parts in it. Honestly it still sounds like a secondary side boost leak rather than a solenoid - you've already tested the function of most of your solenoids by measuring the vacuum or pressure going to the actuators. Does the CRV hold pressure on the bench? Have you done all the FSM bench tests?

I've got 160k miles on all my solenoids except the lone 2nd TCV solenoid that mounted above the rat's nest. They are stupid reliable in my experience, especially considering the abuse they take from heat and duty cycles.

Well the TCA solonoid works. Guess I'll try the rest but I have low hopes. I've tested the CRV by applying vacuum to the small port and it works fine. That's what I read in the FSM. I don't have a fitting to try the larger ports. I haven't found any busted lines or anything. I'm kinda bummed. If I had a torn diaphragm in CCV wouldn't it be open and I'd be getting the boost? Is that not how it works?

Thanks!

I can't remember on the CCV. You can remove the top vacuum line going to it, push the rod in while you have a finger over the nipple, and release the rod. If the rod moves a little then stops, then when you take your finger off the nipple it finishes the travel then it's OK.

If it freely moves back and forth with your finger on the nipple the diaphragm is broken.

I think you can do a similar test with the turbo control valve. Also make sure your vacuum/boost lines going to the turbo control valve aren't swapped around, I think that will do weird stuff.

Dale

I read this whole thread and started reminiscing of my past turbo troubles. I don’t miss it lol.

Did you ever pressure test the system? It could be the o ring on the y pipe since the car is still sequential.

I was thinking that too. Or a blown out gasket/loose flange at the rear compressor to y-pipe connection.

In addition to eliminating every option for secondary leaks OP needs to be methodical with every single component: does it do what it's supposed to do on your work bench and is it getting the proper pressure/vacuum signal it needs during operation. Chasing symptoms and throwing parts at this system is too confusing in my experience.

FWIW I have never actually had a boost problem I could attribute to an actuator or the control system. It was always something stupid I did plumbing-wise or a mechanical problem (also something stupid I did).

I know it is the more expensive and definitely time consuming way, but IMO I usually start from the source and then work backwards to solve a car problem, once the easy fixes don't work. You can troubleshoot for days on end if you start further down the chain and still not find the problem, as in this case. That is why, I believe, at this point you should pull the UIM, check every boost solenoid and replace IMO(don't want to do this again and you rule this out), then check every vacuum line or replace if old and not silicone, then recheck every check valve for function(make sure it is the right direction), check the pressure and vacuum tanks(see they hold pressure and the lines are good), and lastly check all the wiring going to the solenoids, particularly if it is an old or original harness. If the problem is then resolved, you are done. If not, then one by one check each of the peripheral items, such as the actuators themselves, etc.
Mike

I'm back! I've had to stop working on the car for a few weeks due to work and family obligations but I'm still dealing with it. Thanks to all of those who have offered advice, it's keeping me going!

I've pulled off the UIM to check the solonoids. The turbo control works. I pulled off the "A" solonoid and of course it broke the "a" and "b" ends off so I couldn't test it. I did hook power up to it and it clicked but I can't test if it holds pressure. It looks like it's the same as the "C" solonoid so I was going to use that but I think that one is failed. It doesn't hold any pressure or vacuum. The "C" was off the car so it couldn't have been my problem before but I don't want to install a broken part. I'll just order a new one. The "H" solonoid works. The purge control also work. I'll build a pressure tester tomorrow to see if there is a bad seal somewhere.

Thank you from staying with me!

If my wastegate was stuck wide open would that be enough to bleed all but 3 pounds of boost?

The actuator or the door itself? Why do you suspect this is the case?

Either. I suspect it because of the sound after 4500rpm and the fact that I'm running out of ideas.

Have you physically inspected the secondary turbo?

It may be damaged. Pull the intake pipe off and see if there's oil, damage or excessive play in the wheel. Have you verified the gasket and connection between the y-pipe and the secondary compressor? The leak may be there.

An open wastegate would boost more than 3 lbs.

You're gonna drive yourself crazy trying random shit. There are too many pieces of the twin turbo puzzle to leave it to guess work. You need to understand and test each component... confirm 100% that it functions as needed on the bench / on the car by hooking up the mityvac. Then tee into each signal line while driving and watch the gauge to see that the components are getting air pressure/vac when they should. Start with the components related to secondary boost...

I second checking that y-pipe to secondary compressor flange and turbo itself. It would be a weird failure, but makes sense.

Everybody's least favorite incompetent mechanic is back! I have bench tested the following solonoids: turbo control, pre control, wastegate, purge control, C, and H. They all work. The pressure and vacuum tanks have no leaks. The CRV works. When I say they work I mean they all hold the required pressure/vacuum and release when sent a signal. I pulled off the y-pipe and it looks fine to me. What am I missing?
https://cimg5.ibsrv.net/gimg/www.rx7...b864bdcef.jpeg
https://cimg0.ibsrv.net/gimg/www.rx7...d10e8e8fe.jpeg
https://cimg5.ibsrv.net/gimg/www.rx7...347914de5.jpeg

Right now I'm on the fence of just going single turbo if only to solve this problem.

Replace that O-ring between the 2 Y-pipe halves. The oily stuff looks like you have had a leak there.

Also, check the actuator on the Y-pipe. If you put your finger on one of the nipples, push the rod in, and let go of the rod, the rod should stay in until you take you finger off the nipple. If it pops out, the diaphragm in that actuator is torn.

How is the 90 degree rubber elbow going to the charge relief valve on the back of the Y-pipe? It looks original, they typically crack and leak boost or get so hard that they don't seal and leak.

Dale

Yeah, you've been blasting boost out of that flattened o-ring for some time from the looks of it. That oil and dirt doesn't build up there for no reason. If that o-ring is done, there are probably other parts like those Dale mentioned that need replacing.

Looks like you left the rear part of the y-pipe on. Several of us suggested that could have a leak at the secondary compressor flange.

If that doesn't solve it... and I doubt the o-ring will since that o-ring is on the primary side of the system.

Have you teed into TCA press&vac, CCV, CRV while driving? Note that you could have avoided a bench test of those solenoids by teeing in while driving and confirming press/vac signal. That also tells you if the lines/hoses going to those actuators are intact - in my mind it's a better test.

Did you test the TCA itself with a mity vac? Not the 2 TCA solenoids (there are 2)... test the actuator itself. Same with the other actuators. CCV, CRV.

Think of it like this... confirm the actuator is getting a signal while driving by teeing in with a gauge. Then confirm that signal moves the actautor with a mityvac.

Again, you said after transition you are venting boost under the hood. You can hear it. That't a big clue to look at secondary side and/or be very suspicious of the CRV function & hoses.

Thanks for staying with me guys! I'm taking a lunch break so here is an update. I tested the turbo actuator (big one under the car). It took about 4.5-5psi to get it to move on both the pressure and vacuum side. The CRV hose is brand new and has no splitting and the CRV itself works (tested with a Mityvac Silver kit, like a good boy). We've measured the CCV pressure before and know it's getting the right amount. I pulled off the vacuum side, closed the valve, put my finger over the nipple(ha!), Let go and it stayed open until I moved my finger. So I know the diaphragm is good.

I don't think the gasket for the part of the y-pipe that actually connects to turbo is bad because then it would never build up enough pressure to open the CCV. But what do I know? Any other ideas or tests? I cleaned up the y-pipe and my current plans are to put it all back together and drive around. If the y-pipe gets dirty again, there's my leak. If not, I'll.....I don't know, be sad I guess?

Any other ideas? Thanks!

I would get a new O-ring, that is leaking for sure. Since you're that far in I would check the gasket between the back half of the Y-pipe and the secondary turbo. The original gaskets were paper and failed, the updated ones are metal and pretty much never fail. Also worth being sure that there's no old paper gasket stuck on the flanges and that it's bolted down well.

Dale

Done. Looks okay to me, what do you think?
https://cimg7.ibsrv.net/gimg/www.rx7...aff175edd.jpeg

Looks good. Does the secondary compressor spin freely or contact the housing?

That's the metal gasket so you are good there. Do want to make sure the Y-pipe bolts down flat on both flanges and nothing is pushing it off the flange.

Dale

At least from my limited experience the metal gaskets can wear out, like a crush washer does eventually. Quite a few of mine leaked at least a little when I tried to re-use them, no matter how careful I was torquing everything down.

When I put new gaskets in all the leaks stopped completely, and those gaskets are pretty cheap.

Not saying that's your problem, just sharing my experience. From your picture, that gasket looks like its been there at least a little while.

The compressor spins freely. I'll bolt it all down tight. Right now my only hope it that the y-pipe o-ring is letting out all my boost. I'll order a new one and drive it tomorrow to see. If that's not it then I really don't know at this point. Thanks again for the help!

Once you get the O-ring in we may need a re-cap of what you've tested and what the current symptoms are on your next test drive.

Also, I read earlier about you doing the KOKO test. I don't think that test works with the PowerFC.

Dumb question - you wouldn't have accidentally turned off the sequential turbo control on the PowerFC?

Dale

https://cimg9.ibsrv.net/gimg/www.rx7...4b80fe12e.jpeg
What a day! A real rollercoaster. I'll skip the details and get to the results. I put everything back together and, low and behold it runs. The plan was to get it running and go for a test drive to see if the O-ring was the culprit. But then I got RX-7ed. I see smoke coming from the primary turbo. It's coming from below the banjo oil bolt. I can't tell if it's from the bolt or below it. Now it has always smelled burny around this area and sometimes I thought I saw smoke from the corner of my eye. Of course whenever I payed attention, got a light, put it in the shade, it was totally fine. Not this time. I put the car up and the back of the turbo looks wet. Is this normal if the car sits for four months? I assume there is no way to know without pulling the whole thing out. Have my twins decided to die, is this the sign to go single? Did my adequate bank accounts anger the FD Gods?!!

I plan to see if it's dry tomorrow, fire it up and see what it does. Maybe drive it. Sorry this took such a turn but I'm just following the car.

Thanks again!

Oh, Dale, never a stupid question with me. The sequential is still turn on.