Audi A1 TDI Power Loss Points to Injection System Issue

I had a very similar experience with my Audi A3 2.0 TDI from 2015. Having some basic experience with diesel engines, I first suspected fuel injector issues, but it turned out to be more complex. The symptoms matched yours exactly, increased fuel consumption, reduced power, and rough running. The check engine light was also constantly illuminated. After checking the car, my workshop discovered that a previous timing belt replacement had been done incorrectly. This caused slight misalignment of the camshaft, which in turn affected the fuel injector timing and created cylinder pressure problems. Since this was a consequential error from the previous repair, they fixed it at no cost (0 Euro). To properly diagnose your issue, it would help to know: Current mileage, When was the last timing belt change? Are there any unusual sounds from the engine? Have you noticed any black smoke from the exhaust? Any recent repairs or maintenance work? The symptoms you describe could point to various issues, from simple sensor problems to more serious mechanical concerns. A proper diagnostic scan would be the first step to identify the root cause.

After visiting my workshop for diagnostic tests at 87787 KM, they found the intake manifold was damaged and letting in excess air. They also discovered carbon buildup affecting the turbocharger performance. The vacuum test confirmed irregular pressure readings. During the latest service they cleaned the intake system and replaced faulty sensors. This resolved both the engine knocking and poor performance issues. The check engine light is now off and fuel consumption has returned to normal. I had previously worried it might be a timing belt problem, but thankfully it was just the intake system causing trouble.

Thanks for the update on your A1. My A3 actually had similar issues a few months after my timing belt incident. The root cause in my case was also carbon buildup affecting the turbocharger and intake manifold, making me wonder if this is a common weakness in these engines. The workshop did a thorough cleaning of the entire intake system at around 85000 KM. They found significant carbon deposits restricting airflow and causing those irregular pressure readings we both experienced. The engine knocking disappeared right after the service. A blocked intake manifold combined with turbocharger issues definitely explains the symptoms we both faced, poor performance, high fuel consumption, and warning lights. The total repair cost was 650 Euro for cleaning and parts. Good to hear your fuel consumption is back to normal. These problems are definitely less severe than potential timing belt or head gasket failures, which I initially feared when facing similar symptoms.

Thanks for sharing your experience with the A3. The intake manifold and turbocharger issues you mentioned match my situation perfectly. Getting the system cleaned made such a difference. Just received my invoice, total repair costs came to 580 Euro including parts and labor. Much better than the potential 2000 Euro+ I was worried about when thinking it might be timing belt related. The mechanic showed me the carbon buildup they removed from the intake system, it was shocking how much had accumulated. They suggested doing preventive cleaning every 40000 KM to avoid these issues recurring. They also checked the head gasket and piston rings while they had everything apart, but thankfully those were all in good condition. My engine now runs like new again, no more rough idling or power loss. Going to follow their maintenance schedule strictly from now on since it seems these TDI engines really need regular intake system cleaning to prevent performance issues.