I am using an AEM UEGO and laptop to read AFRs. I had originally changed out the O2 sensors since I was using a lot of fuel. I could not get a toyota brand O2 so I used a bosch replacement. It turns out I had a fuel leak at the return, so it was not the O2 sensor.

Since then I have fouled plugs from running too rich, and I was getting a dip at idle after coming to a stop as well as rich conditions.

I decided to replace the bosch o2 with the stock sensor that came with my 205 engine. That corrected everything. So the bosch replacement does not seem to perform as well as oem.

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Coldiron (Cold - Iron)
1992 Celica Gt4 RC Conv. St205 swap

http://www.noritoy.com

Teh ecu was probably having a *bleep* moment with bad values from the generic sensor and going into a safe mode

You really need a dvm on the sensors to understand what's happening

Also did you reset the ecu after the swap. If not it's probably still running off bad learned corrections which might be why the afr isn't immediately stable

I reset it since I swapped back in the old sensor. The car ran good before, but it runs great now. I think I can move on to other things I want to sort out on the car.

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Coldiron (Cold - Iron)
1992 Celica Gt4 RC Conv. St205 swap

http://www.noritoy.com