Geza,

What is the temp of your model thermostat?  If it is the lower temp one,
it opens sooner rather than later and thus the engine takes longer to
heat up because all the coolant starts circulating and getting cooled by
the radiator loop.

I still think this problem is due to something else, not the O2 sensor.

If I understand correctly, it is the temp measurement from the Temp II
sensor to the ECU that sends the engine into closed loop, not the temp
of the O2 sensor.  Don't have time to look that up and verify it, but
think it is correct.

Also, that a part is new doesn't necessarily mean that it isn't the
culprit.  I once had two or three consecutive bad thermostats in an old
Chevy.  Engine was reading hot, but the radiator was cold, but it had
new thermostats.  So, you might need to check the thermostat.  If the
water pump was not working well, the engine would heat up sooner, not later.

The attached files have lots of info on FI system problems and one set
focuses on the O2 sensor.

Have you checked out your idle stabilizer unit?

But read the files before going to all this trouble on the heated O2 sensor.

Sam

--
Sam Walters
Baltimore, MD

89 Syncro GL, Zetec Inside
85 Westy Weekender
85 Mercedes Benz 300D Turbodiesel - to become veggie oil powered

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