Symptons of bad oxygen sensor

The oxygen sensor is replaced for free in the USA only when the
vehicle reaches it's first 80 000 miles regardless of the age & number
of owners as stated in the factory owner's manual in the maintenance
section, some Toyota dealerships are reluctant to replace it for free
if that happens contact the Toyota regional head office for your
region where they will give your local dealership 48 hours to comply.
On average the oxygen sensors should be replaced every 6 years or 100
000 miles or so which ever comes first as stated in the owner's
manual, warranty booklet and factory service manual.

Symptoms of a bad o2 sensor are poor gas mileage, hesistation in
acceleration, worse emissions, and in severe cases after the stat
opens the engine can no longer maintain stable 750 rpm (with manual 5
spd tranny) idle and the engine begins to stall.

The 02 sensor is designed to function once the vehicle has warmed up
which is about after 10 minutes where the thermostat begins to open at
190 or 195 degrees Ferenheit depending on thermostat then the vehicles
ECU system enters what they call a "closed loop system" then the
exhaust manifold's temperature reaches 400 degree Ferenheit (I
think)that's where the sensor starts to do it's job which is usually
when the thermostat first opens up then the oxygen sensor senses the
ratio of air to fuel and sends a signal back to the ECU then ECU
compensates by increasing or decrease the open time for the fuel
injectors to pump fuel.

So usually the problem of stalling shows up after about 10 minutes of
driving or so. Many folks think that the o2 sensor is bad but an
exhaust leak can cause excess oxygen to enter the exhaust system
thereby fooling the sensor into thinking there is too much oxygen,
there are other problems that could cause it to give false reading
such as a vacuum leak.

If you discover that the o2 sensor is bad and it is not under warranty
then from my/others experience/research purchase an o2 sensor in the
following order:

1)Toyota (NipponDenso now called Denso)
2)Denso aftermarket (Same as original but sold aftermarket)
3)NTK (oxygen sensor division of NGK)

Available at:

http://www.1sttoyotaparts.com/partscat.html (10% shipping by Fed Ex or
free shipping with $100 & over speak to Roger at 1-888-271-3948)
http://www.toyotadiscountparts.com (free shipping with $100 & up)
http://www.Toyotaparts4U.com
http://www.toyotaofplano.com
http://www.densoaftermarket.com
http://www.densoproducts.com
http://www.ngksparkplugs.com (use coupon code "dodgetalk" to get extra
10% off)
http://www.rockauto.com

before you replace the oxygen sensor soak the 14 mm brass nuts with
any of these deep penetrating oils several times for several hours:

1)PB Blaster
2)Liquid Wrench
3)Kroil Oil
4)Aero Kroil & Sili Kroil
5)Toyota Rust Penetrant or High Performance Penetrating lube
6)Rust Check
7)Fluid Film

the first ones being the best, also if you decide you need new ones
here is the Toyota part for the exhaust manifold (brass) nuts #
90179-10175 (14 mm socket)

Sidney(R) (tm)
Repairs TV's,VCR's,home/car audio out of my apartment
E-mail:sidneybek(at)yahoo.com
Dartmouth,Nova Scotia
Canada

http://web.archive.org/web/20040312120415/www.herald.ns.ca/cgi-bin/hom...isplayp

http://web.archive.org/web/20040229023255/http://www.herald.ns.ca/cgi-.../home/d

http://groups.google.com/group/hfx.forsale/browse_thread/thread/43940c...231ab85

http://www.iwaynet.net/~nesda/May02/May18.html
http://www.iwaynet.net/~nesda/SonyAudMod.html
http://www.repairfaq.org/sam/sonytune.htm#sonynoi
http://www.iwaynet.net/~nesda/Oct02/Oct028.html
http://www.iwaynet.net/~nesda/Oct02/Oct029.html
http://www.iwaynet.net/~nesda/Oct04/Oct041.html