URQ quirqiness

[Louis-Alain Richard]

> My 83 is still being a bit of a puzzle. That's the nicest way I can
> put  it.
> Symptoms: Frequency Valve operation comes and goes _very_
> sporadically.
> 
> Actions so far:
> New hall sender
> New O2 sensor
> new wire from ECU to FV
> 3 different FV
> 3 different (and verified) temp sensors
> 3 different flywheel sensors
> 3 different ECU's
> Air temp sensor readings within spec
> replaced fuel pump
> 
> For my money, that pretty much covers the bases. No amount of wire
> wiggling (including the back of the fuse panel) will re-produce or
stop the effect.
> Where do I go from here?

If all the electrical bits are OK, it must be air that is flaky (because
the FV try to adjust the mixture). Maybe the ECU and its components are
just doing their job ?

So, my long shot is the small vacuum hose that goes through the firewall
from the intake to the ECU.

Another way of eliminate suspects: 
Maybe you can monitor the O2 sensor via an air-fuel ratio meter (Martin
Pajak will be proud of you, :-)) and observe the FV buzzing and see if
they are in sync ?

Hope this helps,

Louis-Alain