Why unplugging the 02 sensor makes my 3.2 run smoother..

[nene]

I replaced my 02 sensor a few months ago and recently noticed that if unplugged, the car ran smoother in general, no flat spots upon revving. Just a few notes, I did check all vaccum lines, adjusted valves, new sparkplug cables and adjusted base idle. Maybe running rich, although it doesn't smell like it.

Thoughts?


Serge

[LJ851]

It goes into default mode which is richer and generally runs better since these cars were pretty lean originally.

[E Sully]

Does the idle drop when you remove the oil cap? If not, you may still have a vacuum leak.

[Joe Bob]

Or the O2 sensor is dead.

[yelcab1]

Just a guess since I am not the engineer who wrote that software.

It is because the feedback loop is broken, and the ECU is no longer trying to adjust the mixture. It is working off a set fuel map and it runs better.

[nene]

That for your the replies:

Yes the idle drops when removing oil tank cap. The original 02 had the same side-effects as the new one, that's why I changed it.

Generally as the engine warms up, the car runs good with the sensor connected, but does run better without it.

Serge

[cgarr]

I noticed the same thing with mine until the sensor got good and hot.

[shahram]

What is your idle RPM with O2 sensor plugged and unplugged?

[nene]

The idle remains the same under both circumstances.