MavrickFD

If im not driving my car too hard and not going WOT as soon as I change gears, I boost fine. As soon as I drive hard like I'm racing and having the peddle to the floor, the sequence of events goes as follows: When Im in 2nd gear boost levels are fine. When I shift into 3rd, I boost straight to 4 or 5ish where it'll stay for about a half a second then quickly shoot straight to 10 or 11ish like a late reaction. When I shift into 4th, it'll boost to 4 or 5ish, where it'll stay, and I feel a loss of power. As soon as I let off of the peddle I hear a "bbbrrrrrrrrr" sound. The only way I can describe the sound is, it's like when you spin a wheel too fast on a toy car and it vibrates. Kind of a retarded example but It's all I can come up with. Im guessing a boost leak of some kind but not really sure where.

mad_7tist

still seq?

MavrickFD

yea still seq

dubulup

failing check valve? Lazy solenoid...sticking precontrol/WG actuator

just some things to look at.

yuichiror

iTrader: (1)

Yeah Flynn, that's what I'm thinkin'...

jd to rescue

iTrader: (3)

May want to check the vac lines to/from the pressure tank and the vacuum tank. May also want to check the tanks for leaks. These affect the performance of your transition actuators.

MavrickFD

I checked under the pressure chamber (the black box above the alternator) and the green piece was not connected to anything. Is it suppose to be like that? Also, whats causing the "brrrrrrrr" sound. Thats why I was thinking it was a boost leak and is air venting

dubulup

green piece should be connected to the other half which is white...one vacuum line on each half.

dubulup FTW

brrrrr sound - maybe that green piece vibrating into the top of the pressure chamber

jd to rescue

iTrader: (3)

What I think you are referencing is a check valve. There should be a hose leading up to the check valve and one going away. If one end is not attached to anything or a nipple is broken off then you have probably found your problem. Some one can probably pull up a vacuum hose diagram to help you out. There is also one on the inside hood of your car and one at page F-10 in the FSM.

MavrickFD

Just to make things more clear, the 2 green check valves, off to the right side of the pressure chamber when looking at the car from the front, is connected. The other green piece, which I guess is another check valve, is coming off of the pressure chamber. The small hose is connected to the nipple that is in front, closest to you, and is routed right underneath the pressure chamber. At the end of the green piece is what looks to be foam. There is another hose thats black and is around the same area which also has foam at the end of it. It LOOKS like the pieces should be connected together, but they don't connect. I just want to make sure we're talking about the same check valve. Sorry if I'm being too vague and not providing enough info. Kind of sucks that I don't have a digital camera to show you guys.

yuichiror

iTrader: (1)

Got pics? Else I can try to have a look at it Wednesday. I think there's two green/white check valves, then one metal one and there's at least one line that just connects to a filter. Kinda hard to conceptualize what you're talking about, but I'm full of beer...

MavrickFD

Haha. I'll try and come through wednesday and show you what i'm talking about

quicksilver_rx7

Look at the vacuum hose diagram. That should explain a lot. If you don't have one, do a search on here to find it.

Joe

dubulup

my bet is it's a check valve cracked in half and the pressure chamber isn't pressurizing from the y-pipe.

MavrickFD

That's exactly what it is. Thanks to the diagram, the check valve that I was talking about was the one in between the pressure chamber and the Y-pipe. At one end of the hose is the green piece, while the other one is missing the housing and is just the black tip with foam at the end. Thanks for the help fellas. Anyone know where I can get one cheap? Malloy?

z28_SS

the thing about the sequential twins is that it will always give problems and will never work properly on almost all FD's out there. One easy way to eliminate this is to just go Single or better yet LS1 swap.
End of boost issue.

dubulup

check for sale section...

dgeesaman

iTrader: (7)

Thats' definitely a check valve split in half. It will affect your boost, no doubt.

You could probably try to superglue it back together around the seam, but it's worthwhile to just buy some new ones.

yuichiror

iTrader: (1)

If that's the case Flynn, you should go ahead and PM DaleClark. He sells viton check values.

quicksilver_rx7

I beg to diifer. If the system is repaired correctly and maintained properly, it should be trouble-free for a long time. If understood and maintained properly, the sequential system can be one of the most rewarding experiences to owning an FD. It's not hard to repair and maintain, if you understand how the system works, are aware of it's limitations, and have the immeasureable amount of support that is obviously available on this forum (and you know a thing or two about working on a car).

Joe