[Supras] bad oxygen sensor likleihood

[berniek at technicaldevelop.com]

Rocky and others had written about running rich for the first few 
minutes of operation.  I doubt if the problem is the O2 sensor for at 
least two reasons:


1.  The engine is operating in open loop for the first few minutes of 
operation until the sensor heater gets it hot.


2.  Rarely does an O2 sensor really go bad.  The link below is for 
simple testing, on or off the car.  I did both of mine (JDM and stock 
'91) off the car with the propane torch method covered in the article 
and both came out fine.  One of them is now in the rebuilt engine and is 
working fine.  Beware that connector types changed between '90 and '91 
('90 was round, '91 was a rectangular connector).  Either can be spliced 
to either connector. 

http://www.mr2.com/TEXT/O2_Sensor.html


I've had more trouble with the cold injection timer switch in the 
thermostat housing than anything else regarding poor cold running or 
starting, but in my case, it stayed on for too short a time period.  If 
any doubt exists about it not opening fast enough, pull off the time 
switch connector immediately after starting the car and see what happens.


          Bernie