RE: High boost problems on '91 200QW-solved?

[Phil Rose <pjrose@servtech.com>]

>Date: Mon, 24 May 1999 01:31:28 -0700 (PDT)
>From: "James A. Desveaux" <desveaux@ucla.edu>
>Subject: RE: High boost problems on '91 200QW-solved?
>
>I think I solved the high boost problems with the 200QW.  Thanks to Phil
>Rose, Scott Mockrey, Dave Aukerman (sp?), and others for their input.  The
>plug wires all looked fine, with no evidence of arcing anywhere.  The
>distributor cap and rotor looked fine, and I didn't notice any carbon
>tracking.  I did, however, notice some oil in there, but not a lot.  I did
>check the small diameter vacuum hoses, the ones that connect at the back of
>the intake manifold.  Phil bet me a cup of coffee that the culprit was the
>vacuum line to the turbo bypass valve.  I pulled it, blew through it to make
>sure it was clear, reattached it to the bypass valve, and then attached my
>vacuum pump to make sure it held vacuum. It did.

But did it hold pressure? Did you disconnect and test the hose _only_ from
the IM end? Unless that hose is _also_ pulled off the bypass valve, being
able to blow through it easily (or at all) is not a good sign.  Unless I
misunderstand what you've described, it sounds as though your bypass valve
isn't (wasn't) able to hold a positive pressure from the so-called vacuum
hose. That would imply an internal leak that could bleed off boost.  As
Scott M. has pointed out in the past, that "vacuum" hose is best called a
"control" hose, since it passes both vacuum and pos. pressure from the IM
to the bypass valve. However I can't imagine, if this was the case,  why
your boost would suddenly seem to be OK again. I hope your problem doesn't
reappear soon, but these "immaculate" cures don't inspire confidence about
the long-term, do they? BTW, when I replaced my defective bypass valve, it
held vacuum, but not positive pressure.

> So Phil, as a compromise
>I'll send you that Starbuck's Frappucino coupon I got in the mail.  I like
>mine black and bitter anyway.

But so do I. Frappucino is for __________ drivers! (fill in the blank) :-)


Phil Rose				Rochester, NY
'91 200q				mailto:pjrose@servtech.com
'89 100