O2 Sensor

[sc300rye1]

I have to replace both o2 sensors and I was wondering just what they do and where they are located at in the engine. Does any one know how to do this? I just got the tool off of ebay

[AWJ]

What year is it?

http://mkiv.com/manual/1995_electrical_man.../95elec_082.JPG

[sc300rye1]

It is a 1992.

[The Grinch]

An o2 sensor does just what its called. it measures o2's from your exhaust flow.

The ecu reads the o2's signal by voltage. from this it gets your motors air to fuel ratios for that moment. the ecu then makes adjustments to optimize your air to fuel. If your sensors go out most cars will just run rich and lose gas mileage.

they should be located just after the collector (the place your exhaust manifold comes together). I believe an OBD2 car will have another just after the catilitic converter.

Get a can of PB Buster, they may be stuck.

[Lucifer]

The O2 sensor simply compares the amount of oxygen left over in the exhaust gas to the oxygen outside. If there is a lot of oxygen in the exhaust, the computer interprets that as a lean condition and adds more fuel. Ideal combustion occurs at about 14.7:1 air/fuel ratio, this is called stochiometric and there should be no oxygen left over and only minute amounts of unburnt fuel and other combustion by products (carbon-monoxide and carbon-dioxide).

All O2 sensors work the same. They generate a voltage in a range from .9 volts if the exhaust is rich (low oxygen), to about .1 volt if the exhaust is lean (high oxygen). .5 volts is stochiometric. The engine computer reads and counts each time the sensor toggles past .5 volts and adjusts the fuel ratio accordingly. Before the O2 sensor can start generating a signal it has to reach an operating temperature of about 600º F. The two, three, and four wire sensors just have an integrated pre-heater and extra ground wires.

An O2 sensor has a porous ceramic tip coated with rare metals; once the tip begins to glow it starts to generate and fluctuate voltage rapidly. O2 sensors naturally slow down with age and this affects the computer's ability to react quickly and keep up with changing fuel needs. Leaded fuel will coat the tip of the sensor and and clog the porous ceramic eventually causing it to react slowly. Silicone is instant death to an O2 sensor. Use only low-volitile RTV silicone gasket sealer on the engine. Never, ever, get any WD-40 (silicone lubricant) or Armor-All (silicone tire dressing) on the O2 sensor tip or outside shell. If you drop a new O2 sensor or simply over tighten it, you may as well throw it away because the ceramic is easily fractured. Always be sure to use anti-seize on the threads (new sensors come with it). Torque to about 30 ft lbs.

[AWJ]

Okay, 1992 has 3 o^2 sensors. Two in the exhaust manifold (should be top side) and one after the pre cats and before the main cat if I recall correctly. I'll need to verify. Just take your time with it. Check www.mkiv.com - check the factory service manual links and find the naturally aspriated or non turbo 2jz-ge info. This should help you out until you can find a copy of the manuals for yourself.