O2 sensor bias

Kurek, Larry LKurek at ocfexch2.ocf.anl.gov
Fri Aug 28 14:34:20 GMT 1998


Do tell.

How about a little info on how you did this, and what other "symptoms"
you may have observed. Maybe the ECM is thinking that the combustion
temps are too high (isn't the O2 sensor output affected by temps?), and
opens the EGR more to try to lower it? How high were you able to bias
the O2 before you ran into problems with the EGR? 

Thanks!

Larry



> -----Original Message-----
> From:	John Wickerham [SMTP:ibeme at glasscity.net]
> Sent:	Friday, August 28, 1998 8:32 AM
> To:	diy_efi at esl.eng.ohio-state.edu
> Subject:	Re: O2 sensor bias
> 
> I'll add my bit to the discussion about O2 sensor biasing.  I
> have a Chevy S10 Blazer with 4.3 Liter V6, TBI system.  It's
> one of the '7747 ECU's.  I played around with biasing the O2
> sensor high so that the ECU would think the engine was running
> rich when in reality it was not.  The idea was to lean out the
> mix under conditions when the ECU was looking at the O2 sensor.
> 
> I know for a fact that as a result of biasing the O2 sensor high
> on this vehicle, that the ECU changed the EGR flow as well
> as the pulse width of the injectors.  If you go too high with
> the bias, the ECU triggers a fault and tells me that the duty
> cycle on the EGR has exceeded 50%.
> 
> The point I'm making is that biasing the O2 sensor will do more
> than shorten the pulse width of the injectors.  There may be
> other side effects that negate what you're trying to do.
> 
> Later,
> John



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