[alfa] 164 Grand Challenge - Taming of the shrew round three

["Karl Chen" <karlcchen@xxxxxxxxxxx>]

OK. Now I am getting into the most difficult challenge as far as I am
concerned.



This is the symptom:



My 92 164S stayed in over rich fuel mixture all the time.

I monitored oxygen sensor output; it stayed at above 0.8V to 0.9V all the
time.

This is the third new oxygen sensor I put in now, all previous oxygen
sensors dead from over rich black exhaust.

If I disconnected O2 signal from ECU and let a little bit air leak into
throttle create lean mixture condition, O2 output

voltage dropped to below 0.1V.  So that proved oxygen sensor is still good.
Without disconnect O2 sensor,

leaking air into throttle has little effect on output voltage, apparently
the ECU try to compensate by stay at rich mixture,



On the other good cars I have, when at 2500 rpm, I will see O2 output cycle
between the 0.2V to 0.8V about once

every second.  But on this 92 164S, the output voltage doesn't not change at
all at any high RPM.   Only when throttle

is fully released will it go below 0.2V for about one second, then it is
back at 0.9V all the time.



Please Help,

Karl
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