URQ intermittant duty cycle

Joshua van Tol josh at spiny.com
Mon Nov 14 21:46:20 EST 2005

The O2 sensor signal goes south because it's reporting a lean  
mixture, which is caused by the frequency valve quitting. It sounds  
like you either have a bad frequency valve, a bad ECU, or bad wiring  
between the two. I'd bet that you'll find that the ECU has some cold  
solder joints, probably around the driver for the frequency valve.

On Nov 14, 2005, at 8:12 PM, DGraber460 at aol.com wrote:

> My relatively new to me URQ has baffled me when it comes to getting it
> dialed in. I have used every trick that worked on the wrecked car  
> and it  responds
> but will not completely dial in.
> Tonight I monitored the O2 sensor and found that when the idle (or
> acceleration) goes weird, the O2 signal goes to zero as well. Cool  
> I thought, so  I
> replaced the O2 sensor and thought I had my smoking gun. No Joy. It  
> still acts
> up, with the duty cycle going to 99 and O2 signal going to steady . 
> 003.
> When everything is good the O2 reading varies from 0.2 to 0.7 and  
> the freq
> valve buzzes away. When things are bad the FV goes dead quiet.
> It is sporadic, and on some instances revving the engine will bring  
> it  back-
> sometimes not.
> What could cause this? Is this the dreaded ECU duty cycle signal  
> failure?  If
> so, why would the O2 signal go south? Do I have 2 equally bad O2  
> sensors?
> Wiggling all the wires has no effect.
> Dennis
> Denver
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