No Cat, No Oxygen sensor.

[h100vw]

If the injectors were leaking badly, I think you would find it hard to start. I wouldn't be concerned about the 4 electrode plugs as long as the heat range is correct.

I think if you were to get hold of a MK3 wiring diagram you could find out the colour of the lambda probe wires and see if you can find a plug with them in.

I had a MK3 16V in the UK and it was carp on petrol, barely ever getting to 30 MPG. A friend had owned one and he often saw 40 plus on the motorway at 70mph. Sometimes up to 50 on a back road run.

Anyway, sometime a couple of months after I bought it, I went to install some suspension and found that the lambda probe was just tied to the heat shield over the exhaust. The PO had de-catted it and not bothered to put the probe in the exhaust. I fitted a cat I had in the garage and immediately got another 10MPG everywhere. The ECU would have been seeing a massively weak mixture and tried its hardest to richen things up.

Gavin

[ryana89]

On a cold morning my car takes no more than 3 seconds to start.... Id imagine that doesn't count as hard starting

Just went out for another check around the engine bay and FINALLY found the plug that the O2 sensor harness would plug into! (atleast I think so?)
Feel rather stupid that I couldn't find it before, but ohwell.



The wires going to the plug


It was hinding around the back of the 4th inlet runner on the manifold, had 4 wires going to it, so a 4 pin plug?
May get a quote from an exhaust shop to see how much it would cost to weld a bung for an O2 sensor to sit in, into the exhaust.


Just had a sneak around GAP, all MK2 O2 sensors are either 2 or 3 wire. MK3 O2 sensors are 4 wire

[GOLFBALLS]

It looks pretty obvious to me that this car has had a 2E conversion. That 2E engine was never offered anywhere in the world in the mk2. In the process, they have put in that custom made exhaust and left that 4-pin lambda plug hanging.

It also explains the other wire plug you found in the scuttle tray, and the alternator is probably the mk2 one because of the ease of re-wiring.

If that actually is the correct ECU for that engine, then its gonna be a very confused little computer without that oxy sensor in place and like Gav said, is feeding loads of fuel in coz its getting no reading.

Remember, this car came from South Africa, which raised my suspicions of it being standard/factory immediately. I've seen quite a few imports around from SA, all of them were "tinkered with".

You should be able to sort that out with a standard 2ltr mk3 lambda??

Cheers

[ryana89]

You should be able to sort that out with a standard 2ltr mk3 lambda??

Cheers

Thats what I hope but heres the plug end of a 8V 2.0L MK3 O2 sensor connector plug


The problems is immediate,
Differant pin set up with that pin on the end so far from the others... with a tab in the middle.

And I can assure you thats its a very confused computer!
15+ ltrs/100km aswell as occaisionally coughing black smoke on cool start ups

I also have no clue what that 2 wire plug in under the rain tray, any ideas?

Thanks

PS: Im also curious as to what will happen when I plug an O2 sensor into a ECU that hasnt had one for a LONG time......

I can assure you that is a very confused little computer!
15litres per 100K aswell as coughing black smoke on cool start-ups.

[GOLFBALLS]

I wouldn't necessarily go off the pic because sometimes they are inaccurate.

Give your Brissie hsy branch a call and see if they can sort one for you.

I'll have a look at my girlfriends mk3 2ltr when she gets home to see what that plug is too mate.

There shouldn't be any issues with the ECU once you plug it back in to a lambda, thats what it was designed for!

Good luck!

[ryana89]

Thanks mate!

[jayjay]

gavin's right. even the latest of late model mk2s would probably not have come with 2E. You find those motors on super early mk3s here and Seats.

That ECU is from a golf 3 or seat... someone did the sneaky back in capetown.

[Spyda]

I think the O2 sensor you posted is for american 2L motors.
I had a 2E o2sensor and plug (cut off a wreak) and it was exactly the same as what you have one your car.

Very strange combinantion. I wonder how its all been wired in to the ecu.

[GOLFBALLS]

even the latest of late model mk2s would probably not have come with 2E. You find those motors on super early mk3s here and Seats.
.

No Mk2 ever came from the factory with a 2E.

[ryana89]

Went to an injector specialist this afternoon and 'apparantly', an oxygen sensor does not affect how much fuel is used (and it can only be mounted past the cat), apparantly thats the job of the knock sensor because a knock sensors determines how much fuel is used.....

Also my car does 2000rpm at 60km/h in 4th gear and this is apparantly very unusual/bad and means my cars has been fiddled with.
Also everybody online in forums like these are apparant complete novice backyard mechanics that don't have a clue what they're saying........

I just love informed people who think they can give advice

I will NOT be going back there ever again

PS: Golfballs, when does your Girlfriend get home?

[Spyda]

Went to an injector specialist this afternoon and 'apparantly', an oxygen sensor does not affect how much fuel is used (and it can only be mounted past the cat), apparantly thats the job of the knock sensor because a knock sensors determines how much fuel is used.....

Also my car does 2000rpm at 60km/h in 4th gear and this is apparantly very unusual/bad and means my cars has been fiddled with.
Also everybody online in forums like these are apparant complete novice backyard mechanics that don't have a clue what they're saying........

I just love informed people who think they can give advice

I will NOT be going back there ever again

PS: Golfballs, when does your Girlfriend get home?

LMAO!!! What an idiot.

Now im not a specialist and im not a great back yard mechanic either but as far as i know the knock sensor is to do with timing advance and retard and the o2 sensor looks at the oxygen and carbon in your exhaust fumes so the ecu can map the fuel properly. If you put it after the cat then whats the point if its going to be monitoring filltered fumes?

As far as i remember on my mk2 the o2 was before the cat. On the extractors i just fitted to the mk1 the holes for an o2 sensor are before the cat. On the pile of exhaust manifolds i had in the garage, the o2 sensor was before the cat.

If there is anything unusal about your revs in different gears its probly because of the gti short ratio box. I would have thought that gears and revs are more to do with your ratio than your engine.

[ryana89]

LMAO!!! What an idiot.

Could not agree more.

Every chance I tried explaining like what you just said above, I got fumed at and told "We've had 20 years in the buisness, we know these things. What makes you think you would know the secrets of the trade"

Im tempted to go back and hand her a some photocopies of Bentley and Bosch fuel injection manuals.
As for the gear ratio buiesness, How the F*ck does would she tinkering with an engines electrics affect final drive raito

[Spyda]

Could not agree more.

Every chance I tried explaining like what you just said above, I got fumed at and told "We've had 20 years in the buisness, we know these things. What makes you think you would know the secrets of the trade"

Im tempted to go back and hand her a some photocopies of Bentley and Bosch fuel injection manuals.
As for the gear ratio buiesness, How the F*ck does would she tinkering with an engines electrics affect final drive raito

Thats the problem with people who think experience is the key. If youve been doing something badly for 20years your just going to be realy realy good at doing something badly.
How the hell is it a secret to know what part does what in your car?

I had the same problem with a mechanic, he took $100 off me and fixed the wrong thing. It turned out i was right.

[GOLFBALLS]

Yep, get it sorted and go back and show them how off the mark they were. Then tell them to keep away from VAG cars!

[ryana89]

Not to sound rude but,
Should I take the plunge and buy a 4 Wire MK3 oxygen sensor from gap?
Or buy a generic 4 wire Oxygen sensor through my workplace (Supercheap) and simply hardwire it in?
ACA Oxygen Sensors: Universal
The generic one (OX204F) can even come with a flange ready to be welded into the exhaust, but I really have no idea if a Digi 2 computer is gonna like a "generic" sensor.


Thankyou