Rough Engine Idle: AFN Causes & Fixes

Hello!
My car's check engine light is on again. Today, I drove off the highway and then, while accelerating on a country road, the following happened: A brief hesitation, followed by the ABS, preheating, and parking brake warning lights illuminating. This happened several times before it went away. In the last few kilometers before reaching the garage, the engine ran very unevenly, as if it were only running on three cylinders. The sound is still somewhat normal at idle, but it sounds unhealthy as the RPM increases. It starts well sometimes, and poorly at other times (right after each other).

Background: Approximately 3000 km ago (at 67000 km), the timing belt broke. This caused damage to the valves and hydraulic lifters. I had the cylinder head professionally rebuilt, and all affected parts were replaced. I did the removal and installation myself. Everything seemed to be working perfectly.

Today, I checked the following:
Error memory: Empty.
Injection timing: According to the TDI timing checker, it is still perfectly accurate.
Camshaft timing: OK.
Visual inspection of the timing belt: OK.

My concerns are now leaning towards the fuel injectors (at least those would be relatively easy to replace), or a stuck valve (which is bad, I don't want to have to disassemble everything again). I'm just not sure how to explain why all the different warning lights are coming on.


What do you mean?

Annoyed greetings, Arnd.

Hello, it's possible that a valve spring has broken, because you mentioned that it's running on three cylinders. This might not be noticeable at idle.

@Autopilot

Have you already read the error codes? Could there be a short circuit in the wiring harness? Is relay 109 working correctly?

Best regards, WarLord.

Okay, here's the solution to the riddle:
Ein Pleuellager hat gefressen und dabei reichlich Späne verteilt. Der Zapfen auf der KW hat nun 0.25mm 'Untermaß'. Der Kolben schlug unter den Zylinderkopf. Die Zylinderlaufbahn wurde auch in Mitleidenschaft gezogen. Werde dem Motor nun eine Generalüberholung angedeihen lassen. Ob das Ganze nun ein Folgeschaden des Zahnriemendramas ist, oder eine Quittung für 60000 km mit Chiptuning, werde ich wohl nie erfahren. Achja: Gesamtlaufleistung war 70000 km. Topqualität also... (This seems like an incomplete sentence or a fragment. A possible translation, depending on context, could be: 'opquality, so...' or 'opquality, therefore...')

Best regards, Arnd.

Probably a timing belt issue.

Best regards, WarLord.

Hi.

Did your camshaft remain intact when the timing chain broke?

I'm actually looking forward to the resumption of operation of my AEL this weekend.
Unfortunately, I'm not 100% sure whether the crank mechanism is in good working order.

Best regards, KAi.

The camshaft was undamaged after the timing belt broke.

Best regards, Arnd.