Nothing happens when I disconnect O2 sensor...

[Thieu]

what gives? I've been running rich for a while (~20mpg +/-)... and I have the dreaded "shaking at idle / burbling exhaust" etc... So as my car is idling, I disconnect my O2 sensor and not a single sign of change from the engine... Should I replace it?

[zero.counter]

Have you checked the ECU to see if it was throwing codes?

[Thieu]

Have you checked the ECU to see if it was throwing codes?

Not yet... but doesn't this mean that my O2 sensor isn't functioning?

[zero.counter]

Not yet... but doesn't this mean that my O2 sensor isn't functioning?
You have a point, but then so does the ecu throwing an O2 sensor code.

[Maeda]

Sounds like your running closed loop mode (AKA SHITTY). Just throw a turbo on it and dyno it like me. :coolugh:

[F3600]

usualy the o2 sensors does nothing at idle ..

the o2 sensors is used only when you are in light cruising something like that ...

[Thieu]

Hmmm... what else would make me run rich... Basically the only things I haven't replaced in my engine bay are the TPS, MAF and FPR... the O2 sensor is about 6 months old, but I may have been sold a defective one... who knows?

[Var]

a fuel problem. you shouldnt do anything at all before you read the ECU codes.

[Thieu]

I read the codes... 55... which means... no codes...

I tried getting a reading from the TPS. The car will only idle at 750-800 (still popping from the exhaust and shaking) with the TPS reading .3V to 3.6V (supposed to be .5V to 4.0V). When I get it set correctly, the car runs fine but the idle drops down to 500rpm when I come to a stop and then slowly rises to 1400rpm and idles there...

So my guess is I need a new TPS... what do you think?

[tak-]

my o2 sensor wire got burned off. is that bad?

[Var]

my o2 sensor wire got burned off. is that bad?


do you really have to ask such a question. if it's burned off like you said that means the ECU isnt getting any input from the O2 sensor..so is that bad? i dont know. i think we need a poll on this one

[idlafie]

what gives? I've been running rich for a while (~20mpg +/-)... and I have the dreaded "shaking at idle / burbling exhaust" etc... So as my car is idling, I disconnect my O2 sensor and not a single sign of change from the engine... Should I replace it?

To get an idea of what the 0xygen sensor does, click on the following link: (found after a quick Yahoo search)

http://www.aera.org/Techside/oxygen_sensors_101.htm

Always a good idea to test components PRIOR to replacing. To test the O2 sensor, go to the www.240sx.org website & click on the FAQ button. Put the ECU into diagnostic mode, then rev your engine to about 2-3K for about a minute or two. The LED on the ECU should start to flash. If it flashes more than 10 times in 10 seconds the 02 sensor is still good.

As for your engine running rich, have you considered checking your Engine Coolant Temperature Sensor unit? How bout cleaning out & replacing that "reed" in the IIAV valve / AIV valve...forget which one it is. You might want to check the vacuum line running to the fuel regulator also. Try wiggling the wires at the Throttle Position Sensor / Mass Air Flow Sensor / Engine Coolant Temperature Sensor - you're checking to see if you have a short in any of those sensor wires. If you do then that would cause your running rich/bad idle. Also, check to see if the ground wire between the firewall & the engine block is still attached. The ground wire is on the driver side of the engine above the O2 Sensor and is grounded on the firewall to the left of the brake booster. Hope this helps..
Diego
'95 SE

[Thieu]

I replaced my O2 sensor and no change. I replaced the ground above the O2 sensor a while back so that's good. I also replaced the coolant temp sensor a while back so that's not it.

If I play with the MAF sensor connector, the engine will kinda surge and whatenot for a second. Nothing happens when I do that with the TPS connector.

I ordered a TPS sensor online for cheap so we'll see if that changes anything...

Also, I replaced all my vacuum lines a short while ago, so I doubt that's the problem.

I took out my AIV and EGR too...