Hi All,

I've got a 3.5L TJ Magna and I'm getting the Headers I bought off Blackbeard fitted today. Exhaust shop busted the 02 sensor trying to get it out of the stock pipe. Anyway they said when they went to remove it from the car it wasn't even plugged in!!!!

Probably why my fuel consumption has been up around 13L/100km for so long.

Anyway, Where does the o2 sensor plug in, and how do you get to the plug?

its under the carpet on the passenger near the place where u access the ECU. have a look under the car where it goes. access it from the inside the cabin.

its under the carpet on the passenger near the place where u access the ECU. have a look under the car where it goes. access it from the inside the cabin.

Thanks mate.

There are some pics of the connector itself in this thread (http://www.aussiemagna.com/forums/showthread.php?t=35169)

There are some pics of the connector itself in this thread (http://www.aussiemagna.com/forums/showthread.php?t=35169)

Thanks cthulhu.

THE RPW Headers are now Fitted. Seems the Exhaust shop was able to repair the damage to the O2 sensor thread so no increase in charge. Guess they didn't want to suffer one angry magna owner on a Monday arvo. Anyway, Car sounds awesome although I think it's a little confused that it can breath now and has input from an O2 sensor...I wonder how long it has been unplugged for...:confused:

Oh, And I can hear that High pitched rasp that people talk about, combined with a deeper growl. At Idle it almost sounds like it has the burble off a V8.

:bowrofl:

Hope you're happy with them Mark.

Busting the thread on the O2 sensor when being removed from the factory piping the first time must be a common problem...... happened to mine but like yours, the exhaust shop was able to fix the thread up so it was re-usable....... luckily haven't had any problem with it since.

:shock: @ it not being plugged in at the other end though!!! I would have thought the car would have gone into "limp mode" if it wasn't receiving a signal from the O2 sensor. I wouldn't have thought the ECU would be able to function in closed loop mode without it :confused: .

:shock: @ it not being plugged in at the other end though!!! I would have thought the car would have gone into "limp mode" if it wasn't receiving a signal from the O2 sensor. I wouldn't have thought the ECU would be able to function in closed loop mode without it :confused: .
From what i've heard the ECU just runs in default mode, where pre-loaded settings are used. So it works, just not as well.
Should see some better fuel economy now :).

Hope you're happy with them Mark.

Busting the thread on the O2 sensor when being removed from the factory piping the first time must be a common problem...... happened to mine but like yours, the exhaust shop was able to fix the thread up so it was re-usable....... luckily haven't had any problem with it since.

:shock: @ it not being plugged in at the other end though!!! I would have thought the car would have gone into "limp mode" if it wasn't receiving a signal from the O2 sensor. I wouldn't have thought the ECU would be able to function in closed loop mode without it :confused: .

Thanks Mike I am Happy with them.

No engine lights...Nothing at all.

Still I'm disappointed I didn't do it myself... I had the stock headers loose and everything preped, but I just couldn't put any more force on that O2 sensor without busting it. So Everything was tightened back up and I got to doing household chores instead. - mowing, edging Etc... (The missus was happy about that anyway)

From what i've heard the ECU just runs in default mode, where pre-loaded settings are used. So it works, just not as well.
Should see some better fuel economy now :).

Unless I like the sound of these headers too much lol

There are some pics of the connector itself in this thread (http://www.aussiemagna.com/forums/showthread.php?t=35169)

And some pics in THIS (http://www.aussiemagna.com/forums/showthread.php?t=35438&page=2&highlight=sensor) thread also. :D

And some pics in THIS (http://www.aussiemagna.com/forums/showthread.php?t=35438&page=2&highlight=sensor) thread also. :D

Much nicer than mine :D And without the four thousand wires from my E6X getting in the way too.

Hope you're happy with them Mark.

Busting the thread on the O2 sensor when being removed from the factory piping the first time must be a common problem...... happened to mine but like yours, the exhaust shop was able to fix the thread up so it was re-usable....... luckily haven't had any problem with it since.

:shock: @ it not being plugged in at the other end though!!! I would have thought the car would have gone into "limp mode" if it wasn't receiving a signal from the O2 sensor. I wouldn't have thought the ECU would be able to function in closed loop mode without it :confused: .
I don't know about the third gens but with the second gens they changed the engine management in about 1993 so that the oxy sensor wouldn't give a fault reading. Have no idea why, probably because it isn't an integral part of the engine management system.

The oxy sensor is only used when the engine goes into a closed loop cycle. This occurs when the load and rpm remain fairly constant, ie cruising, so the ecu stops using the fuel maps and uses only the oxy sensor to get the air-fuel ratio as lean as possible without causing detonation.

The oxy sensor is only used when the engine goes into a closed loop cycle. This occurs when the load and rpm remain fairly constant, ie cruising, so the ecu stops using the fuel maps and uses only the oxy sensor to get the air-fuel ratio as lean as possible without causing detonation.

No it doesn't. It uses the oxygen sensor to get air/fuel ratios as close to stoichiometric (14.7:1) as possible for the most complete combustion and therefore cleanest emissions.

Are you sure? I'm fairly certain that in closed loop it tries to lean out the engine as much as possible. I know that newer engines like the GDI ones definately do as they achieve air fuel ratios of up to 40:1

Are you sure? I'm fairly certain that in closed loop it tries to lean out the engine as much as possible. I know that newer engines like the GDI ones definately do as they achieve air fuel ratios of up to 40:1

Ah, I see what you might be getting at.. some (most?) cars have a light load lean-out condition where if they're at light load and it hasn't changed for a couple of minutes, like having cruise control set on a highway, they'll lean-out slowly to save fuel.

But regular closed loop, like when you're stopped at a set of lights, or at light load cruise before the other mode kicks in, the computer aims for stoich to reduce emissions.

edit: keep in mind the 3rd gen magna doesn't have a knock sensor so getting really lean is dangerous too

A motors peak power will be at 14.7:1, if you go higher than that the torque will die off. Past about 15.5:1 the torque starts to die off very quickly so you wont see a petrol motor run leaner than that, otherwise you would have to offset the torque loss with a little extra throttle, negating fuel econemy.


Ah, I see what you might be getting at.. some (most?) cars have a light load lean-out condition where if they're at light load and it hasn't changed for a couple of minutes, like having cruise control set on a highway, they'll lean-out slowly to save fuel. I have never heard of this, and if they did lean out then power would taper off quite quickly and heat would become a problem.

yeah 3rd gens dont give off an engine light when the oxy sensor goes bust. I dont know how long mine was gone for until i picked up on it when trying to source a different problem.

A motors peak power will be at 14.7:1, if you go higher than that the torque will die off. Past about 15.5:1 the torque starts to die off very quickly so you wont see a petrol motor run leaner than that, otherwise you would have to offset the torque loss with a little extra throttle, negating fuel econemy.

I have never heard of this, and if they did lean out then power would taper off quite quickly and heat would become a problem.

No, a motor's peak power isn't at 14.7:1. Where'd you get that from? There isn't a mass produced car on the planet that is programmed for 14.7:1 at its peak power point.

Also, from an Autospeed interview..



Under cruise conditions, the VN-VPs cruise on 14.7:1, while VRs onward use a lean cruise function. Lean cruise kicks in once coolant temperature is over 80 degrees C, you're travelling faster than 68 km/h, the engine is spinning at between 1600 and 2800 rpm and manifold vacuum is between 40 kPa and 60 kPa absolute (the VS-on works on an airflow meter signal). Once 150 seconds is timed out under those conditions, the air-fuel ratio will lean out one point every 0.15 seconds. They're set up to run as lean as 16.5:1 - but only at that light load cruise situation. You can't be driving on and off the throttle.

^^^^Yeah that's what I was talking about cthulhu. With the knock sensor are you 100% sure there isn't one? Cos I was having a read through the 3rd gen workshop manual and it mentioned that there was one.:confused: