Nuebe Question. Will s4 t2 run at all without O2 sensor?
 

Alright just got this thing rebuilt after blowing it from running lean on a shitty pump so I am super paranoid about running lean.

I am using the s4 jspec harness and ecu and some of the wires do not match up and someone had some hack job running to the o2 sensor before. This was fine and dandy but since I did the rebuild I couldnt remember what it plugged to so I ran my own wire to the ECU.

And seeing as how I still cannot get a reading from the temp sensor I wonder if I am doing any better with this.

If the thing could run what would happen? I do not want to run lean on this shit.

It will run with out the o2 sensor if I remember right all that will happen is make the car run a little bit richer.

+1 the o2 sensor leans it out at cruise (1500rpm to about 3500), so without mileage will be low, but it'll run fine.

the ECU and the temp gauge also get their readings from different sensors, so I wouldn't be too worried about that either.

you should get that fixed though just as a precaution. the temp sensor is on the back side of the block near the oil pressure sender and the clutch slave cylinder (driver side) make sure it's plugged in.

As a fail safe when a o2 sensor stops working (sending a signal) or is not present the ecu automatically runs the car at full rich as to keep from pre-detonation(pinging).

But the car isnt really running right as well. It would turn on and if you keep your foot on the gas it would stay on, but as soon as you let your foot off the gas it would immediately shut off and wont start cause it gets flooded. So that means the car is running rich, and means that the o2 sensor isnt doing shit. Am I right or there is something else going on?

At idle, the oxygen sensor does little if anything to keep the engine running I believe.

The 02 sensor is not used at idle. Period.

The ECU runs in open loop (not using the O2 sensor) at idle, and under moderate to heavy acceleration, and during decelleration (where it goes intentionally lean). The O2 sensor is active only under steady cruise or light acceleration.

If the O2 sensor is not present (i.e. open circuit in the wire to the sensor) the ECU will do one of two things: it will either 1) correctly discern that the sensor is missing, and default to a rich condition, or 2) incorrectly interpret the high impedance as a valid O2 sensor signal and try to adjust the mixture on it, in which case the car will run terribly. I found it will do one or the other almost randomly after each shutdown and restart when there is an open circuit.

Oddly, in the condition where it runs terribly, it throws no code. When it runs well (on the default rich condition), it will thow a code 5, but then who checks codes when the car runs great? Mine even passed smog without the O2 sensor working, but the hydrocarbons were above average, and the cat ran hot and eventually was destroyed internally.

If you are concerned about the sensor not playing with the ECU for some reason, a single LED checker will verify it, using the center two pins in the six pin check connector. It is on when the ECU sees rich, and off when it sees lean. If all is well, it should cycle about 8x per 10 sec at steady cruise. If that is working, it verifies the sensor, the wiring, and the ECU all in one check.