Originally Posted By: HerrStig
Originally Posted By: eljefino
Lazy 02? Popping in and out of closed loop? You wouldn't know and the car wouldn't care.
This causes a lot of trouble with 96 to 2001 Toyotas and won't set an OBD II. Another tip off is a car which runs lean after being shut down long enough for the engine to cool. The O2 hangs up on the warmed up engine (closed lpoop) reading although the engine has cooled enough to need a richer mixture. The engine stalls and backfires until the sensor flips to sending the proper signal. A blast of wide open throttle often causes to sensor to flip. Replacing the sensor solves the problem. This problem seems to happen in the spring and fall when it isn't very cold but cold enough to require the richer open loop mixture for a short period of time after a restart. Input from the water temp sensor apparently isn't enough to override the O2.
This open loop closed loop dance is all to save some PPMs of HC by leaning out the mixture as soon as possible.
It always amazed me that the dealer parts changers, without an OBD code, had NO clue as to what was going on the ONE time I took a car there. The O2s are not cheap, for a Bosch, Denso, or NTK, but if the problem is bad wnough you ought to change it out. The sensor involved is the one in the exhaust manifold, no the one after the converter which is there to monitor the cat, not provide mixture adjustment feedback. The V6 engine is not
as subject as there are TWO sensors, one for each bank.
O2 sensor on this car is very easy to change, you only need a crescent wrench of spark plug size (14mm?) and go on rockauto to buy an aftermarket one for around $26 + shipping. Any aftermarket new one will be better than a worn out one that is bad enough to give you rough idle, but of course, NTK and Denso would be ideal for a Japanese car.
