New Oxygen Sensor, Fuel Economy Worse?

[anarklov3r]

How you going guys.

I just replaced the Oxygen Sensor in my VN/VP Wagon because i was getting O2 Sensor Errors from the computer.

I was getting 14 - 15 ltr/100km (around 330km just before the red section of the fuel gauge), and was idling shockingly (sounded and felt like it would stall some times..)

So i switched it over with a new one, error went away, idles much nicer so all sweet i guess.

At first i thought it had done the trick (hit 120kms at 7/8ths of the tank left), then it just started dropping super fast!

I just filled the tank and got 300kms outta it (16ltr /100km!) Should this be happening? It doesn't make sense to me.. Car feels like it drives better, but fuel economy is worse!

Should I have to reset the ECU/Computer ? If so is there a way to reset it without having to disconnect the battery and leave it 30mins + ? Its a pain to get my central locking going again and re configure my stereo.

Any ideas would be great!

[Vt-Brrrlina]

to reset your computer look under the bonnet at the fuse box there is a smallers thing of fuses in front of it

undo the engine fusible link - cant remember which colour it is - pull that one for 10 secs or so to reset computer (note 1 of those fuses wont come out so dont force it )

as for mileage technically u should get better mileage but depends on the error code u got - one code is for lean running which the computer just dumps tons of fuel to rectify and the other is for too rich - and it leans out the car to compensate or something like that

[Scooter79]

I know in the VS you can remove the engine relay under the bonnet. VN might be similar.

[anarklov3r]

i believe the code was o2 sensor missing / no signal or something along those lines.

It was pretty shot when i pulled it out. ill show a pic of new vs old

[h0Ld3n`VN]

this is weird for me too..
while my o2 sensor was off (disconnected) because it didnt match the s2 loom
i was getting real good economy 8.5ltrs/100ks

now with the new sensor its odd getting abit crap around 12ltrs/100ks??????????

and thats mostly surburn/city driving

i dont get it

[Scooter79]

this is weird for me too..
while my o2 sensor was off (disconnected) because it didnt match the s2 loom
i was getting real good economy 8.5ltrs/100ks

now with the new sensor its odd getting abit crap around 12ltrs/100ks??????????

and thats mostly surburn/city driving

i dont get it

It may have something to do with a ground wire. I don't know the details but I know 'surfwagon' who is a member on here knows quite a bit about it. He might be the one to help.

[mrtdk59]

Have you checked the O2 sensor is plugged in the right way.
I had a similar problem a while ago and replaced the O2 sensor.
I got about 250km out of a full tank of fuel ....... F**k
It ran like sh** for a few weeks before a mechanic friend checked it.
He told me I had plugged it in the wrong way.
He just pulled the plug out and turned it around and plugged it back in.
Fuel economy and power returned immediately.
Worth a go if all else seems to be OK

Also my car smelled like it was running very rich on fuel mixture, exhaust pipe was black at the tip. I even had a oily stain on the rear bumper.
My 2 cents worth - hope it helps

[greenfoam]

O2 sensors isn't normally the cause of bad fuel economy, it's normally only a small part of a run down car. The ecu's temp sensor and the fuel regulator can be major issues

[Morton]

And I'd be doing the temp sensor first, because that's the cheapest and easiest