Mixture changed now not starting when cold.

[jslootweg 0]

Having failed my MOT for emissions I have replaced my lambda. I then put my car on my gas tester and it was showing CO of around 12%. So i set my CO reading to 2% (after having removed the re-breather pipe) using the 3mm screw on the metering head. The car was running like a dream, smooth running, better mpg, the works. I was well chuffed with myself. Until the next morning when i tried to start my motor. It starts up straight away, but instantly dies, i can't catch it on the throttle either. I can only fix it by setting the CO high again. Its almost like on my old Mini when i didn't have the choke pulled right out. So i thought it was probably my cold start valve not working. But thats firing, with a nice even spray pattern. So i'm wondering what it could be? I have looked for vac leaks and can't see any. Wondering about my ISV? should it buzz when the ignition is on but not running. Because mine is only buzzing when the engine is running. Just wondered if this could be an issue? Any ideas anyone? please don't just say "use the search" because i think i might have possibly read every 2.0l 16v cold start, ISV thread there is. its bugging me, every time i get closer to fixing one problem something gets in my way.

[Crasher 3]

If you reset a 9A like that you alter the base fuelling so now it is ultra lean on cold start. The only way to properly set up a 9A is to have the ECU in basic adjustment mode with a multimeter on the differential pressure regulator (with the VW harness adapter) measuring the current consumption to spec. Did you check for fault codes such as a coolant temp sender?

[jslootweg 0]

No I haven't because I replaced my temp sender about 2 months ago so it should be fine. Where can i get this harness and how much is it? and how do i put the ECU in adjustment mode?

[Crasher 3]

The harness is VAG 1315 A/1 which according to my local dealer is now obsolete so you would have to make one up which isn't too difficult as you only need to intercept the power wire to the differential pressure regulator (it has two wires) and connect the ends to a sensitive multimeter capable of measuring accurately under 200mA. You must have the car connected to an exhaust gas analyser (preferably a four gas) and the ECU is put in basic adjustment mode with diagnostic equipment and VAG-COM is ideal for that but it must be a fully functioning copy, not shareware as I don’t think you can get in basic adjustments with the shareware version. After jumping through a few more hoops, you set the idle co between 0.2 and 1.2% but if you can get the tools together, I will post the process in detail.