[urq] Freq valve failure?

[j.koenig]

My first thought was Idle and/or Full-throttle switch(es), which you may have checked 
already.
Since no other more knowledgeable person has mentioned them...

It's my understanding that their inputs result in fixed duty cycle values at idle and WOT, 
with O2 sensor-driven values in between.  And, of course, you want your duty cycle in 
normal driving to fall below the fixed WOT 'enrichment' value.
The fixed values are somewhere, maybe the IST docs.
Regards,
John


----- Original Message ----- 
From: "Eric J. Fluhr" <ejfluhr at austin.rr.com>
To: <urq at audifans.com>
Sent: Wednesday, April 27, 2011 1:44 AM
Subject: [urq] Freq valve failure?


Gang,

Has anyone experienced a faulty fuel frequency valve that fails when it gets
too hot?

I have been facing a problem with my '82 WX whereby it runs great at first
drive (good stoichiometric
fuel control).   If I stop somewhere and then restart it after a short rest,
it runs exceptionally lean (I have
a wideband O2) at anything off-idle.  At idle, it runs a tad rich.
Recently as it is getting very hot here, it has
started switching to this behavior live when the car is already hot and
heat-soaking sitting in traffic.

I have been testing various subsystems over time, without luck.  Now I am
focusing on the FV.
I have measured the FV duty cycle at the test connector, and the computer is
behaving correctly:
~5% duty cycle at idle, ~92% duty cycle off-idle as it tries to compensate
for the rich & lean mixtures.
Just this evening I decided to disconnect the electrical connector for the
FV while the car was having
this problem, and it behaved approx. the same on the ensuing drive.

So, the smoking gun points at the FV, but have never heard of one failing.
I'm not sure if these can even
be sourced, as it seems to be unique to the WX at least based on part
number.  I'm wondering if I can
use a more readily available model (e.g. MC) and just change the hoses
crimped to the ends.   I need
an inexpensive solution because I have a 20vt waiting in the wings and just
need the car to survive long
enough to prep that.

Any help/info is appreciated.

Thanks,
Eric
'82 Urq, limping along