I've recently been looking over the vacuum lines and found few misconnected vacuum lines. After I've fixed those lines, I've got the primary boost back online. However, when I've test the boost on the secondary, I found out that I have some problems with my secondary boost.

thanks alot in advance!
- Tadashi
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WOT After 4,500 rpm:

- Instantly, it boosted upto 12psi as it should, but with odd whining noises/sound coming out from behind the passenger’s dash.

- After couple of seconds, boost pressure drops from 12psi down to about 7, 8psi.

- During idle, little popping/bubbling sound (vacuum air?) coming out of under the UIM. (I can only hear it if I’m in the car with closed doors or when have my ear few inches away from the UIM.

- Pulled one of the vacuum lines from the pressure chamber after I've got home and I found no pressure. (No air coming out)


Is it possible for you to narrow down the problem with this information above and point me to the right direction?

Here is what I've checked / found out soo far after removing the UIM.

**I’ve checked for possible intake pipe leak but everything looked good.
**After removing the UIM, I found out that the solenoid for double throttle was pluged up with a rubber cap. what would that cause? any relation to the problem I have?

 

Actually you can see it right there in the detail labeled 'MT'. Manual transmission cars have a plastic filter coming off the double throttle.

In any case, it would not be related to the boost problems. To get your secondary working well, you need to verify the vacuum chamber, pressure chamber, charge control, charge relief, and turbo control actuators.

Dave

 

ok so it's not the rubber cap that was causing the boost problem. I'll try to verify the vacuum chamber, pressure chamber, charge control, charge relief, and turbo control actuators when I get a mityvac kit.

 

Wait, is it a rubber cap or a plastic filter? If it's actually a cap that prevents airflow then it is incorrect. Air needs to flow into the back of that solenoid.

Dave

 

Dave,
It was a rubber cap. When my UIM, and alt. was off the car, I replaced it with a vacuum hose with little air filter attached to the tip.
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Trouble shooting the secondary boost problem continues...

- After removing the UIM -
I've zip tied and double checked all the vacuum lines while the UIM was off the car.
I've found out that the vacuum line with check valve connecting to the pressure chamber was loose. It was holding no pressure at all, so I've had that taken care of.

- Test Drive -
I crossed my fingers and hoped that the secondary would function as it should. "Wrong". I still have the problem.

- WOT after 4500rpm -
- Boosts 12 psi
- Boosts drops to 10psi (Boost drops to 10psi but maintains 10psi -not any lower-)
- Whining sound upon WOT, boosting on secondary (my wife said it almost sounds like a robot or motor moving. High pitched boost leaking sound?)

Since my wife came with me to test drive the car, I'm now sure that the sound is coming out directly from behind the passanger dash area.
That pretty much limit to...The Chage Control Actuator, and CRV? I just checked CCA and it is functioning. (Upon idle, the rod goes in.) I'm going to check the CRV later, probably tomorrow. Meanwhile, can anyone tell me what else I should be looking out for?

I will throw in updates as I trouble shoot this problem.
Man, this is starting to get fun!!

- Tadashi

 

ok so I checked the CRV and it's functioning. Here are somethings that I've noticed after the test drive.

- i still have the high pitched whining boost leak sound upon secondary boost.
- after driving, I checked the pressure chamber, and it has no pressure at all. (pulled one of the hose to check if there wasn't any pshhhh!)
- When I pulled out the vacuum hose off of CRV, there was a pressure kept in there. (pshhh!)

does anyone know what does this mean?

 

I think you're getting very close. You need to find the leak in the pressure chamber circuit. The noise you hear could well be the leak where that pressure is going.

Ref: http://www.davidgeesaman.com/rx7/93v...lor.edited.jpg

1st, trace all the blue hoses coming to/from the pressure chamber. Make sure they are connected. 2nd, check the hoses to/from solenoid E in the rack (blue, blue w/ red dots). 3rd, check the blue w/ red dot hoses leading down to the actuator. 4th, check the check valve, and if it fails swap it with the one in the brown color hose.

Normally I'd expect a bad check valve, but the sound you hear implies a loose hose, especially between the actuator and the solenoid.

Good luck. At least you've got good boost thru the range.

Dave

 

i would try and put some pressure einto the chamber itself to see if it will hold.
this will only take 1 min and could save alot of time crimping lines etc..

 

ok, my UIM is out of the car again. This time, it only took me 30min. I'm starting to get good at this.

I've looked around the rat nest once again and there it was, a vacuum line which are hanging, not connected to anything. The vacuum line (on the passanger side) of the(A) solenoid valve pressure regulator control is not connected.

- Where should this vacuum line connect to?
- Can this be the cause?

From the diagram, it does not show where that line leads to.
Here is the picture. I'm speaking of the skyblue vacuum line with pink dots.

 

Actually the diagram sorta shows it. But you can't see that nipple with the fuel rail and ACV in the way.

That should cut down on the lawnmower sound Unfortunately it won't solve the slightly lower secondary. You'll need to find the leak on the pressure chamber circuit to solve that.


Dave

 

Thanks for the picture Dave!

but, oh crap! It looks like I'd have to remove more than just the UIM. Time for me to look for a write up for that...

 

I was just in my garage and it looks like I can get to that nipple by removing the ACV and turbo control solenoid off of the LIM, and leave the rats nest rack, and rest of things as is? I'm just tired and looking for easier way out...

This is going to be the first time for me to remove fuel rails and etc etc...and I don't want to make things worse. Could you please tell me what do I exactly need to remove to get to the nipple? Any write-up or tips to do this?

Thanks!

- Tadashi

 

Remove the ACV only and use a pair of long needle-nose pliers. I actually ground the knurling off the tips of one pair (harbor freight $4 specials) to make it easier to work with deep hoses like this without scratching or cutting them.

It can also help a lot to remove the ignition coil box and slide solenoid A forward (out of the rack) until you have the rear line connected. Then slide it fully into place and rig the front and top nipples.

Dave

 

Those needle pliers worked great! Those 11" straight and bent long needle nose pliers are must have.

I took the car out for a test drive today and my car still have the problems.

Here is the result.

- high pitched whining sound still coming out of the engine bay when the secondary turbo is online.
- Secondary boost only goes up to 8 psi.
- No pressure in the pressure chamber after driving.
- Primary is boosting 8 psi and the boost does not build up as quick as before. (before all this, the primary was perfect. Boosting 12psi without any hasitation. Maybe I didn't put the intake pipes correctly last night.

Only thing that changed after getting that vacuum hose into the nipple was that the boost does not hit 12psi and drop to 8psi. Now, it only goes up to 8psi and remains. I can hardly feel the turbo kicking in now. Sluggish boost build up.

I was pretty sure that vaccum line which was hanging was causing the whining sound but that wasn't it. *sigh*

 

Finally, looks like Mityvac is arriving at my house later today.
Could anyone tell me the procedure as to how to check for the vacuum leak and which solenoids need to be checked (and how to check the solenoids) for the type of problem that I have?

thanks!

 

Do a search with my handle <M104-AMG> and look for the "Dave Disney" test procedures which involves not only a vaccuum/pressure tester but running 12VDC through the solenoids for "sticktion" at 13-15 psi.

:-) neil

 

http://rx7.voodoobox.net/

I've found the site. Thanks!

 

BTW, Dave used one-half of the charge control actuator on the output side to 'hold' the pressure. You can use nearly anything that has some volume - a long section of vacuum hose, the pressure chamber, etc.

I've found that this test is excellent for sorting solenoids to determine the good, bad, and ugly. I like to test all the rack solenoids and put the 'best' ones in the charge control, charge relief, and turbo control locations. Ones like the one in Dave's video, which open/shut very well under vacuum or no pressure, function fine in the emissions locations like FPR, Double Throttle, Switching, and EGR.

Dave

 

maybe I can use my vacuum chamber to "hold" the pressure when I'm check my solenoids.

Is it possible that the "whining" (assuming that it's a leak) sound during secondary boost have something to do with solenoids?

Could you point me to the right direction as to where I should be hooking up the mityvac to check for leaks? (The problem only occurs during secondary is online.)

 

***UPDATE***
After searching for lose hoses, cracked hoses etc etc...
I ended up replacing 99% of the vacuum hoses and
broke one of solenoid nipple, fixing alot of vacuum
hoses which were misconnected and I still could not
find any obvious cause of the problem that I have.
(Symptom: whining sound coming out of behind
the passenger dash upon secondary boost.
Boost drops from 13psi to 8 ~ 9 psi after couple of seconds)

Since I could not find anything wrong from the rat nest,
I decided to go under the car to double check the
intake pipe, which is connected to the turbo again.
It was secured and bolted down tight.
Then, I realized that I have not checked the Y-pipe, which is connected
to the secondary turbo. Uh huh! there it was, a loose nut!
It was not even bolted down at all.


Now, if there is a small leak between the y-pipe
and the secondary turbo it makes sense that
during the boost over 4500rpm, the boost would
leak out of that gap and create a lower boost and the noise.
As far as the just the primary being online,
the CCV (charge control valve) would
restrict the airflow towards the secondary,
so I did not experience any boost leak
or the whining noise coming out from that gap during it's operation.

Does this make sense? am I correct?
Tell me that I've got to the end of this seq problem!

 

It could be the problem, sure. It depends how tight the other bolt was.

Did you get it out for a test drive, or is that coming later?

IME, don't hurry to get things back together once you think you found the problem. The more I hurry to 'wrap up', the more likely I create a new problem, and the less likely the first problem gets fixed. Don't ask me how the odds can change like that, but they do.

Dave

 

Thanks Dave. I'm going to put my car back nice and slow over next week since it's been raining over here, and I don't like to have my car wet.
I'll post again once I test drive the car and find out if that was the cause of the problem.

 

my car is fixed! There was a leak from the connection between the y-pipe and the secondary turbo.

 

Congrats. It's nice to fix something and leave it in better shape than you began.

 

Aint that the truth.