Hi Everyone!

Got a pain in the backside problem..

I've owned my car for nearly 6 months, bought it for £400 with 61k miles. Needed a new clutch and gearbox..

Anyway ive recently been having a problem with the o2 sensor before the catalyst, so of course I changed it, removed the codes went for a drive and had the same problem, juddering missfire etc. Anyway got back home checked the codes and it read o2 sensor faults again. Got another one sent out; still the same problem.

On closer inspection of live data on my reader I noticed that the "o2 sensor bank 1 sensor 2" was reading correctly, continuously changing voltage. The other sensor was reading "o2 sensor bank X sensor X" so I'm assuming the car isn't picking up the sensor. I did unplug the batter leave it for 40mins then start the engine letting it idle for 30mins hoping it would pick up the sensor, no luck! :(

There is defnatley 12v going to the sensor on one wire, a lower voltage on another, one wire being ground, but I'm not sure what the other two are doing..

What should I check for on the other two wires??

Surely I couldn't have had two sensors that are duff?

Perhaps I broke a wire when replacing the gearbox?

(I have had a juddering missfire before but it only happened when cold, once the car had warmed up it was always fine, only recently have I had it missfireing and jusddering when the car is warm)

^ don't know if that meabs anything?

Spark plugs were changed the day I got the car. I have thought about ignition and fuel etc, but if I put my foot down, once I'm above 4000rpm it stopps missing and pulls well.

If anyone has any info on the wiring or any other ideas it would be greatly appreciated!!

Thanks Liam.

What year is the car?

I found this wiring diagram for another member a while ago, but I can't remember what year his car was, so not 100% sure this is correct for your car.

Actually now I think about it I'm not even sure that other fella's car had an AUB engine, so quite possibly not the correct wiring.

See if the colours and wiring destinations match up for this one (which is definitely for AUA/AUB from 1999):

 

 

I'm not sure what you can do beyond checking continuity from engine ECU (J537) pins to wiring connector T6z pins, but that's where I'd start.

Alrght I'll have a look, I have a spair fuel filter lying around that.. I might I

Fit it see if it makes a difference...

So turns out one of the wiring looms has come loose and melted on the egr valve.. I think its the ignition loom that runs to the throttle body and injectors...

Not quite sure what to do, is a new loom going to be stupidly expensive?

I've tied it out of the way and tried my best to tape up the damage. Only one wire seems to have melted through to bare metal.

So I'm going to drive it home and see if its alright if not looks like it's gonna cost me! :(

So turns out one of the wiring looms has come loose and melted on the egr valve.. I think its the ignition loom that runs to the throttle body and injectors...

Not quite sure what to do, is a new loom going to be stupidly expensive?

I've tied it out of the way and tried my best to tape up the damage. Only one wire seems to have melted through to bare metal.

So I'm going to drive it home and see if its alright if not looks like it's gonna cost me! :(

 

Nope it's the loom containing wiring for the Lambda probe you're having trouble with, to fix it, strip off the outer and expose all the individual cables and properly repair any that are damaged or get an auto electrician to come and do it for you.

@sepulchrave the loom 100% is an injector loom, throttle body/ injector's I've traced it back. But thank you for the advice, I will tend to the wiring properly when i have the time!!

@sepulchrave the loom 100% is an injector loom, throttle body/ injector's I've traced it back. But thank you for the advice, I will tend to the wiring properly when i have the time!!

 

I know the loom goes back to them but if you look behind the throttle body on the back right wall of the bulkhead above the ABS modulator you'll see the ECU, all roads lead to Rome remember.

 

The EGR valve is at the front right of the engine attached to the exhaust manifold, the Lambda probes are also in the exhaust manifold under that heatshield, any wires passing near the EGR valve will be heading back towards the ECU via other components along the way, the injectors are at the back of the engine as is the throttle body.

 

So the wiring from the injectors does not come around the front of the engine, it goes back to the ECU. The loom starts out skinny at the front left of the engine and gets fatter as it collects more wires from components along its way back to the ECU.

 

See what I mean?