NefMoto

Hello all,

I have an Audi TT 8N3 with the APP engine. My problem occurred after the engine was replaced. Every cold start is a problem, the car starts normally and after a few seconds it loses revs and dies. After that I have to try to start the car several times until it comes on, then it seems to run only on 2-3 cylinders until it reaches 60-70 degrees. Then the whole thing stabilises and the fault is gone. After that, the car reacts and drives 1A but the cold start phase is a cramp.
My secondary air pump is defective, could this be the cause? Could someone code this out of the .bin file?

Here is a video of the whole issue from start to end: https://www.youtube.com/watch?v=jZcvVkdSs-0

Kind regards

Did you check for Fault codes?

Your coolant temp sensor (the green one or black on early models) is ok?

Also the file attached is the eeprom (95040) not the flash .

Sounds like you have a dead cylinder after you try to restart it the second time. Sounds like you may have that injector locking open shortly after cold start. I would not run the car like that any more, you will damage something by hydrolock. You can hear the fuel washed / low compression cylinder in the second startup.   

@PaulB

There are no fault codes. I don't get it, it's like the car doenst save all the fault codes in my case. Removing the sai should also show me the fault code for that, but nothing in there.
I changed already a lot of stuff (Camshaft, Temp, Spark plugs, Ignition coils etc.).
It helped for about 10 days and then started again.

@_nameless

the engine was completely overhauled. Couldn't the problem be more likely to be a leak? I removed the intake manifold and everything on the fourth cylinder was very wet (the gasket and on the intake), the injector was also very loose as if it was no longer sealing properly. The crankshaft ventilation is tight, the air recirculation valve also works.
Compression was also measured and was also OK.
Does anyone here have the workshop manual so that I can check the vacuum hoses to see if they are connected correctly?
Unfortunately, I can't see any misfires in VCDS either, as the blocks are only empty. Does anyone know if the TT year 2000 had this function at all?

Instead of checking random things, make a pressure test and you will see immediately if the intake holds pressure or not.
If everything was apart this is pretty much required to do.

Pressurize the whole system including the intake manifold with 0.5-1 bar from the turbo inlet, should be enough to see any leaks.
If the pressure test is good, only then start looking for other reasons.

Like I already posted, the compression was ok. So no loss of compression. The other thing is, when the car starts directly with 800 rpm everything run there was no problem and then, when it goes up to 1200 rpm on first start, the problem starts after few seconds of no issues on the start.
If the compression were not there, the car would have to run badly right from the start, but it does not. Or am I wrong? It just takes a few seconds until it starts and then dies.

pressure test != compression of the 4 cylinders  ::)

You said cyl was was wet.  Wet with what?  What _nameless is suggesting seems to match it being wet...

Who talked about compression? Who measures compression with pressurizing from turbo inlet???

I said pressure test.

it's yellow so it must be the fuel that is dripping.

@aef

Sorry, my mistake. I'll put it on the next todo and check the whole thing. Thanks!