What's This/What's It Do?

Phil and Judy Rose pjrose at frontiernet.net
Mon Apr 11 16:20:33 EDT 2005

At 3:24 PM -0400 4/11/05, Kneale Brownson wrote:
>When I had intermittent boost (1.3, 1.4  and then 1.6-1.7 and so on) a
>month ago, Ingo suggested the waste gate frequency valve electricals, so I
>attempted to take this connector
>http://www.pbase.com/kneale_brownson/image/41941930   apart for cleaning.
>Because of the close quarters, I couldn't hold the spring retainer down and
>take the connector off.


>Anyway, what's the connector indicated by the arrow in the pix do and what
>do I probably need to replace?  The fixture onto which the connector goes
>looks corroded at least on the outside, and some of the corrosion appears
>cracked from my efforts to get the connector off a week ago.


  man that's some uuuugly old stuff down there. How old is that car, anyway? ;-)

That of course, is the wastegate freq. valve connector. The wgfv is a 
solenoid valve that regulates the amount of boost pressure admitted 
into the lower chamber of the wastegate ; it has a duty cycle that's 
determined by a fluctuating voltage that's varied by the ecu 
according to its boost map . When the valve fails to operate, its 
default (i.e., no voltage) position is wide open, in which case the 
wastegate will always see the full boost pressure pushing on it; and 
therefore it opens prematurely to limit the boost. By "prematurely" 
is meant there'll be a maximum boost of 1.3 or 1.4 bar rather than 
the normal 1.8 bar. This low-boost mode of failure is a safety 
factor. From the looks of your wgfv "relic", I wouldn't be surprised 
if it needs replacing; however since you report boost is as low as 
1.0 or 1.1 bar, I suspect that something else-- besides (or in 
addition to) the wastegate valve--is misbehaving. You could do an 
audible ("click/clack") test of the  wgfv operation by following the 
ecu "output tests" procedure described in Bentley or in Scott M's web 
site.  A silent valve is a sure sign it needs to be replaced. There's 
also a resistance spec you can check (resistance measured across the 
two terminals of the valve). But look for other problems: a loose 
boost hose clamp, etc.

*  Phil & Judy Rose           Rochester, NY  *      
*        mailto:pjrose at frontiernet.net       *

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