I'm on a bit of steep learning curve at the moment. Does this sound likely. Stock AGU with a centre section exhaust leak the idle is good initially at roughly 1000rpm, but after a few minutes it drops to half that or less and becomes irregular. Could this be the effect of the leak on the lambda probe? I thought it maybe due to the system voltage, but it's made practically no difference.
Hard to guess that over the internet. Run a scan on it and that would help to identify the right cause of concern.
I've been over to it again this morning. It starts to drop from 1100rpm+ gradually 400rpm+ after 5-6mins running there are no engine fault codes apart from the lambda probe and power presumably from having the battery disconnected which then clear. It has 3 year old fuel in it which has been diluted with 12litres of fresh. I was hoping for a smoother path with a more modern car, but it doesn't seem to be the case here lol
I'm almost ready to throw the towel in on it really as time ticks on, but I did find some measuring blocks to check in VAG-COM via another forum which may tell me if there are leaks. I'm juggling at the moment with this, the Golf and looking to buy a stopgap. I was looking a much newer A3, but it turned out to be the year they introduced chains to the TFSI along with a dodgy tensioner.
check under the inlet manifold for those pipe if they're split they will make it sound like crap. also i guess your brake booster pipes are good too? would get the exhaust leak fixed first and make your values in VCDS for the lambda probe are not 'off' then see Though if the leak is past the lambda sensor surely it wouldn't effect the running of the car but make a crappy rattling noise?
Cheers, I'm going to give it a go out of interest with a few other suggestions for future reference, but it's pretty much at the abandon project stage which makes the exhaust is way too involved now. As you say the centre section leak shouldn't really affect the lambda too much. It certainly rattles at 450rpm ish.
Eventually I got back to it and could clearly hear a whistle synced to the turbo as it was now squeezed temporarily into a garage. Things were out of my hands at this stage and I only had time to remove my bits from it before it went for the chop.
If the lambda controller is having to add or take out fuel up to the clip of 25%. you will have symptoms as you describe. Eventually the system will switch off and the fault will appear.
