Rough-Running Audi A5 Points to Intake Manifold Issues

I faced a very similar engine performance issue with my 2006 Audi A4 diesel last year. Having some experience with diesel engines, I initially thought it was just a sensor, but the symptoms matched yours exactly, rough idle, jerking during acceleration, and reduced power. The manifold sensor readings were inconsistent, and after proper diagnosis, my workshop confirmed a leaking intake manifold due to scorching. The engine misfire symptoms got worse over time, especially when the engine was cold. The car manifold had developed cracks causing vacuum leaks, which explained the exhaust smell you mentioned. The complete repair included: Full diagnostic testing, Manifold pressure testing, Replacement of the intake manifold, New gaskets and seals, Labor costs Total cost came to 1180 Euro, but it completely resolved the issues. Before suggesting more specific advice, could you share: Current mileage on your A5? How long have these symptoms been present? Have you noticed any smoke from the engine bay? Did you get any specific error codes read? This information would help determine if your case is similar to what I experienced.

Thanks for sharing your experience. My A5 has 22883 KM and was serviced about 6 months ago. After running diagnostic tests, the workshop found error code P0299 which points to a boost pressure issue. They confirmed a vacuum leak near the intake manifold causing the engine misfire and performance problems. The repair quote seems in line with what you paid. Good to know a manifold replacement solved similar symptoms in your case. Will get it fixed this week to prevent any further engine damage. I noticed the check engine light started flashing more frequently during cold starts, which matches your experience with worsening symptoms at lower temperatures.

Thanks for the update on your A5 situation. The P0299 error code definitely confirms what I experienced, it is a classic sign of boost pressure problems caused by intake manifold issues. The cold start symptoms match exactly what I dealt with before the repair. Given your relatively low mileage, the air intake system should not typically fail this early, but manufacturing defects can occur. In my case, after the manifold replacement, the engine performance returned to normal immediately, and the check engine light never came back. The workshop should perform a thorough manifold sensor check during the repair. When they replaced mine, they also inspected the surrounding seals since vacuum leaks can sometimes affect multiple components in the air intake system. Just make sure they: Test the new manifold for proper sealing, Check all related sensors after installation, Clear all stored error codes, Perform a test drive to confirm normal boost pressure The repair cost is standard for this type of work, and getting it done promptly will prevent more serious engine issues down the line.

Based on all your input, I am now confident to proceed with the repair. The P0299 error code and the vacuum leak diagnosis from my workshop align perfectly with your experience. The cold start issues and performance problems seem textbook for an intake manifold failure. The shop confirmed they will do a complete inspection of the air intake system, including all gasket leaks and related sensors. Their quoted repair price of 1150 Euro matches what you paid, which is reassuring. Good to know the fix completely resolved your issues. My symptoms getting worse during cold starts definitely pushed me to address this sooner rather than later. Will have them do the full testing sequence you mentioned, checking manifold sensor readings, seals, and boost pressure after the repair. Thanks for sharing your experience. It helped confirm my workshop diagnosis and gave me confidence in moving forward with the manifold replacement before any serious engine damage occurs.