RE: Sorting out URQ

["Buchholz, Steven" <Steven.Buchholz@kla-tencor.com>]

The Hall Sender is only used to tell when the engine is at TDC #1, the
timing is set by the computer based on sensors on the flywheel.  I know I've
mentioned the IST documents to you in the past ... they do a great job of
answering questions like this ... You'll also need to put together some way
to measure duty cycle to be able to get to the bottom of the problem.  I've
got a SunPRO unit, but there are others ...

It sounds as though your problem is very similar to the one I'm working
through ... all the plugs consistently black.  The emissions are actually
pretty good off idle, but at idle the mixture goes really rich.  The OXS was
replaced and it made no difference ... the ECU is pushing the duty cycle
down to 0% in an attempt to lean it out.  Others suggested that I might have
a sticking airflow sensor plate ... mine seems to move properly.  My next
task is going to be to test the fuel pressure and control pressure ... there
isn't much more left other than the injectors and the fuel distributor ...

Have you checked the manifold lines that go to the control pressure
regulator?  It is set up to richen the mixture under boost ...

I'll apprise you and the list when I get mine figured out ... let us know if
you get yours done!

Steve Buchholz
San Jose, CA (USA)

> -----Original Message-----
> 
> Tonight tried to set the timing on the URQ. As I moved the 
> distributor back 
> and forth, the timing mark would not move until I reached 
> what seemed to be a 
> limit point going both directions. Is this the much talked 
> about hall sender 
> at work?
> The car is running _very_ rich. If I pull the largest vacuum 
> hose from the 
> intake, the idle increases about 200-400 RPM! Plugs are the 
> blackest/sootiest 
> I have ever seen on an engine that runs. Sounds like open loop mode?
> Where do I go from here to rectify this?
> 
> Dennis Graber
>