Digifant systems

[rubjonny]

It could be the lambda if one is fitted, in the UK we didn't get them on the MK2 as std, not sure if the same is true for Spain.
I'd start with the blue sensor, and work through all the vacuum pipes looking for perished hoses including the one round the back that is usually forgotton about
If it has a lambda, replace it with a quality Bosch universal type, I put a no-name brand one in my gfs Polo and it lasted a fortnight! Bosch one in now and its been fine ever since and flew thru the MOT.

[DarnPB]

Well the bloody thing failed on emissions again today! Is the lambda probe only fitted to cars with a CAT?
When I get back to Madrid (Home) I am going to start from scratch. When I changed the cam belt, I noticed that previously, the lay shaft was in the wrong position according to the book,although the dizzy was correctly positioned. I will start by putting everything in the car as advertised then start trouble shooting again. A friend of mine has an identical car, (my old one that was crashed and he rebuilt) so we can trouble shoot by transferring components as required.
I´m now thinking that the ECU has been played around with. If this has been re-chipped, could that affect the emissions?
 

[rubjonny]

yeah the lambda was only fitted to cars with a cat, its worth getting all the timing reset, don't worry too much about the position of the intermediate shaft pulley, its the dizzy position that matters
My digifant tuning guide also have the procedure for resetting the static timing, and setting the ignition timing correctly

[DarnPB]

Well I've been right through the engine and everything appears to be normal, except the emissions that is. It is now in a garage with specific instructions from me. The compression he said was a little low but perfectly acceptable for the age and mileage of the car. Should be about 160, actually is 140ish. But this should not cause the high CO. He double checked everything that I did and concurred with my findings. The only other thing now to check would be the fuel pump pressure which he is going to do this afternoon.
I suggested the ECU but he thought not.
Any thoughts anyone?
Getting desperate.

[rubjonny]

have you replaced the spark plugs with a decent set of tripple probes, perhaps they are sparking at the wrong time?
It might be worth swapping the ECU, it may have been remapped for a different engine and swapped on at some point.  Also, maybe the injectors are faulty, or have been replaced with a set of the wrong rating dumping too much fuel in...
Might be worth getting the pressure at the fuel rail checked also, perhaps a blockage in the return is holding the pressure up too much?  There is a bolt in the end of the fuel rail, if you remove it you can attach a pressure guage there

[DarnPB]

It had crossed my mind that the ECU had been buggered about with, and the car has a suprising amount of power. The spark plugs are new multi electrode ones. I did the resistance check of the injectors as per the Haynes book of words, and they checked out electrically. The rail pressure was I hope checked today, I'll know tomorrow. I'll keep this all posted, it might help someone else out in the future.
Thanks for all the inputs. Much appreciated.

[DarnPB]

Well the final word is that low compression is causing high emissions. I may be getting the power and nothing externally is indicating that I have a problem, but if the oil rings are faulty, then fuel is finding its way from the combustion chanbers and mixing with the oil. When this gets warm, the fuel evaporates and ends up in the breathing system which is then sucked out by the induction system and back into the combustion chambers, thus inadvertantly causing a rich mixture and high emissions. So the injector and the digifant system is working and doing its job, but obviously cannot detect what is going on downstream of the sensors.
I will try and put it through the test again with the breather pipe disconnected. Apparently, the emissions with the breather not connected are down as low as 0.8. But it looks like I have a project for the summer. 1.9 conversion??? Another post.
 

[rubjonny]

could just be its been overfueling in the past, and the oil is full of fuel.  This is why you need to set the Idle & CO with the breather disconnected and the engine side plugged

Try changing the oil, see if that helps

[DarnPB]

The oil is only 6 weeks old. One of the first jobs I did when I bought the car. I did all the set ups according to your set up posts and the Haynes. I will change the oil again though. For the sake of forty or so Euros, I'm not gambling much. Looking forward to building another engine though, (I'm an light aircraft piston engine specialist) so I'm not too broken hearted.

[rubjonny]

cool, look for 2.0 bootom ends from MK3 GTIs and Passats, engine code 2e