Questions from a newbie

[Shannen Durphey]

Disconnect the O2 sensor, and tune by ear/feel/plug checking.  If there's
a problem in the O2 feedback loop, disconnecting the sensor should make
the engine run better.  If the sensor's responding _correctly_ to
something like a misfire, you need to chase that problem down.

O2 signals should be fairly responsive.  Putting a scope or voltmeter on
the line with the engine running, fuel correct, and in closed loop will
reveal rapidly changing numbers going from low to high peaks.  Testing by
substitution is a good method.  Put a known good part in the car, or
install your questionable sensor in another vehicle.

When the engine is misfiring, there is more free oxygen in the exhaust. 
The O2 sensor responds to oxygen, and it reports a misfire as a lean
condition.  So the ecm adds more fuel, which contributes to the misfire,
which cause O2 to read more lean.

Get your tuning as right as you can in open loop.
Shannen

Drew Skinner wrote:
> 
> Yep, been there done that, it made things worse. Like I said for some reason the ECM is dumping in fuel thinking that things are lean when they aren't. Dunno why but the INT and BLM values don't seem to jive with what's actually going on. I've read tuning tips multiple times now and lately I've been trying to understand the anht_hac.
> 
> Anybody know of a way to test an 02?
> 
> Thanks!
> Drew
> 
> >>> xybertron at cox-internet.com 01/17 12:33 PM >>>
> You take the BLM and divide it by 128.  If it is say 150 then you multiply
> the VE by 1.17 so the VE goes up because you are lean and need more fuel.
> If the BLM is 100 then you multiply the VE by 0.78125 since you are running
> rich and want less fuel.  Following now?
> 
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