[urq] URQ freq valve trigger

urq urq at pacbell.net
Tue Oct 4 00:11:14 EDT 2005

... are you saying that you have two different MAC-02s that behave in the 
same way?  If more than one ECU behaves the same way in your car you may 
want to hook up a duty cycle meter (or oscilloscope) and see if there is 
really a signal there but the pulse width is too narrow for the valve to 
respond to.  Reading your symptoms again, I'm starting to suspect that this 
is really what is going on in your case.  When I had the bad exhaust valve 
on cyl #2 the ECU would drive the duty cycle to a rail trying to lean out 
the mixture ... and the engine ran like crap.  I am pretty sure that I could 
still hear the Freq Valve buzzing in that situation ... but perhaps the 
valve stopped buzzing for me too.  Have you pulled spark plugs to see that 
they all read OK?  How is the compression on all cylinders?

If you just want to get your car running you might want to try unplugging 
the OXS and adjusting the mixture via the airflow metering plate mechanism 
until the engine got a good mixture.  Have you tried tripping the Idle and 
WOT switchessimultaneously at idle?  Does the engine idle smooth out?

... another thought ... what do you know about the OXS that is installed? 
Is it the standard 1 wire unit or is a 3-wire sensor installed?  If it is 
the latter, do you know that the heater is receiving power?

Steve B
San Jose, CA (USA)

> My new to me black #472 URQ 10V K26 is puzzling me a bit. The Frequency
> valve will not work consistently. I just spent the last week removing and
> replacing the down pipe & 02 sensor but no change. The valve itself is not 
> the
> issue. If I plug other known good units into the wiring harness they don't 
> buzz
> either.
> Other than the 02 sensor and the ECU (BTW I'm using the one from my old 
> car
> that worked fine) what other items/sensors could be the culprits?
> If I unplug the 02, the valve buzzes and the car runs  crappy. Plugging 
> the
> 02 back in it shuts down again. The 02 I'm using  was the one from my old 
> car
> that ran great.

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