JSK

Good news, bad news.


Good: looks like I don't need to buy the easily-removed bypass valve, as the spring and diaphragm seem to be in perfect condition (there's a little metal cup still inside that diaphragm that the spring pushes against that's clean too). The turbo-side of the diaphragm had a very thin coat of oil on it - very thin, fyi.


Bad: I guess I still dont' know definitively what the problem IS (even though those crimped wires are indeed suspicious).


Is it possible that the diaphragm can be compromised even though visual inspection seems good? hmmmm...


Maybe this week I'll get to that wiring harness - if nothing else I could make sure to get good fresh wire and make good, solid but temporary wire-nut connections (and get professional assistance for permanent soldering job after they remove harness).


I know I could remove that harness, I just don't have the time (wife not patient at all with automotive endeavors). Sigh. I really had hoped it was a torn bypass diaphragm.


Thanks again for the soldering link and bypass removal link, Oldblue!

Oldblue

You're welcome, let us know!
Maybe to appease the wife, maybe tackle 3 or 4 wires at a time over a few days

DrLoch

FYI, A thin coat of oil on the diaphragm is normal because of the PCV valve system.

RJ_RS_SS_350

JSK, have a look at the bypass solenoid. It's mounted on the intake manifold, the component on the left in this picture


Make sure none of the nipples are broken or cracked, and that the wiring is in good condition.

There's another solenoid, looks similar, mounted to the turbo, just below the bypass valve. This is the wastegate control or boost control solenoid. This solenoid caused my P0234 overboost code. I replaced the solenoid, problem solved.

I still suspect your underboost problem is associated with the bypass valve, if it's not the solenoid itself, then it may be that in your rat's nest are the wires going to the solenoid. Maybe your mechanic or the dealer has the ability to test the solenoid.

I'm not sure if it could be the wastegate solenoid or wiring. If I'm not mistaken, the wastegate is normally closed, facilitating boost. As boost rises, the vacuum/pressure lines and/or the ECM (I'm not sure exactly how it works)will cause the wastegate to gradually open, to control boost. (my solenoid was faulty, so this was not occurring) As a failsafe, the ECM can trigger the p0234 code and command the wastegate to open (and stay open until the next key cycle), limiting boost to about 3PSI.

So if you're getting one solenoid tested, may as well test them both. And if you can determine that the wires to the solenoid are in that rat's nest, then you may be able to fix the problem right there.

JSK

Thanks, RJ - I did look and feel to make sure the solenoid down below on the turbo was in good shape - all the vacuum lines and plugs seemed solidly connected.


I've seen that bypass solenoid too - will double-check its connections and where those wires come from (as in: running through the Rat's Nest?).


Gosh I wish I had a multimeter (and knew how to use it) to test these components. I imagine the proper voltage specifications are in this forum's archives somewhere.
Dr. Loch - thanks, I have read the threads on the oil that accumulates because of the less-than-optimal PVC system, so I wasn't surprised to see the small amount of oil on that diaphragm.
OldBlue - yep, my thoughts exactly: a couple wires per day might work out. I am a night RN (hospice) and have a long stretch of nights in a row, so it may be a few days before I can get to them. (night work is also why my replies sometimes come at 0300 cst, or a day later) (and why MAF cleaner can be difficult to buy - heh)


Again, I thank you all - I promise to keep you updated.

donbrew

multi meters cost less than $10 at Harbor Freight and other stores. Very simple to learn.

Oldblue

Here watch this , and go get yourself a multimeter



http://www.amazon.com/b?ie=UTF8&node=15707471

Amazon, want don't they have??

JSK

Hahahahah -- good point, Don & Blue - good point! Since I've decided to join the 21st century (vehicularly, anyway) I might as well take ownership of what I can. It's time. (just don't ask me to buy a cell phone, ok??)


But for now: off to bed!

DrLoch

What are you doing up so late

RJ_RS_SS_350

JSK - I found this over at css forum, explains what is needed to test the bypass solenoid . 3 posts down from that, another member gives the part number, google turned up this.

So it looks like the dealer might be the way to get the bypass solenoid tested. If it tests good, I would have them also test the boost control solenoid. If the boost control solenoid tests bad, in this thread, 2 members state that this part is a direct replacement.