ur-q EFI - doing it again.....

[glen <gpowell@acacianet.com>]

It's doing it again. (big surprise - few mechanical devices actually heal themselves) After about 1 hour of normal closed-loop operation the ur-q CIS gets funky. I had the % duty-cycle meter on the CIS FV this time. In normal operation the duty-cycle runs about 45-60% and slowly increases from the low end to the high end of this scale as the throttle is slowly opened and then jumps to about 80% and steady open-loop under boost, all very well and good. 

What happened with this observed failure is the duty-cycle slowly increases from 60% to 70-80-90 and then up to 100% duty-cycle and, of course, the O2 sensor reading goes to full rich. It looks like the FV is driving the CIS to full rich when it should not be, but only after 0.5-1.0 hours of normal operation. This failure is intermittent and can come and go after it starts to happen. The coolant temp sensor is a prime suspect, but is new. In previous observed failures without the benefit of the % duty-cycle meter on the FV the O2 meter would indicate full rich and then, for short periods like 5-20 seconds it would indicate full lean. I wonder if this was due to the FV overheating due to running at 100% duty-cycle and shutting down completely and then once cooled down a bit starting up again and kicking the mixture back up to full rich. I have not duplicate this full rich/full lean problem (yet) with the duty-cycle meter connected to the FV, but I bet I will...........

Thoughts?

-glen