RS7 Boost Failure Drains Power and Burns Extra Fuel

Had similar symptoms on my 2019 RS5. The boost pressure sensor was reporting incorrect readings, causing the engine control unit to mismanage boost levels. The turbo lag became very noticeable, especially between 2000-3000 RPM. Initial diagnosis revealed a defective vacuum switching valve, which was causing inconsistent pressure readings. The boost controller was getting wrong signals, leading to poor engine performance and increased fuel consumption. The root cause was a cracked boost solenoid and deteriorated vacuum lines. These components are critical for proper boost control and turbo response. The bypass valve was also stuck partially open, which explained the power loss. The repair required: Replacing the vacuum switching valve, Installing new vacuum lines, Replacing the boost solenoid, Testing the bypass valve operation, Recalibrating the boost controller This was a serious issue that needed immediate attention to prevent potential engine damage. After the repair, boost pressure normalized and fuel consumption returned to normal levels. A proper diagnosis requires specialized equipment to test the pressure sensor and boost control systems. Would suggest getting it checked soon, as these symptoms typically worsen over time.

Thanks for sharing those details about the vacuum switching valve issue. The symptoms and repair steps match what my RS7 was showing too. The intake manifold pressure readings were all over the place before I got it fixed. Quick question: do you remember roughly how much the full repair cost? Also, has everything been running smoothly since, or have you noticed any other boost controller related problems? I want to compare costs since my repair bill felt quite steep. The engine performance is back to normal now, but I like to keep track of these expenses for future reference.

Since fixing the boost pressure control fault with my RS5, everything has run perfectly. The total repair came to 140 Euro for replacing the defective vacuum switching valve. This resolved the irregular intake manifold pressure readings completely. The engine performance returned to normal immediately after the repair, and fuel consumption dropped back to expected levels. I have not experienced any pressure sensor issues or turbo lag in the months since the fix. Compared to what could have gone wrong, the repair was relatively straightforward once the correct diagnosis was made. Having a proper pressure drop test done helped identify the exact problem quickly. No related issues have surfaced since the repair.

Thanks for the feedback. Wanted to share how my situation got resolved. After dealing with the compressor surge issues, I finally found a specialist who properly diagnosed the problem. The intake manifold pressure sensor was failing intermittently, causing incorrect readings to the boost controller. There was also a small vacuum leak near the wastegate actuator. Total repair came to 1250 Euro including parts and labor. The engine performance is now back to factory specs. No more check engine lights or boost pressure problems. Fuel consumption dropped back to normal levels too. Lesson learned, should have gone straight to a turbo specialist instead of my regular mechanic. Would have saved time and prevented the initial misdiagnosis. The proper diagnostic equipment made all the difference in identifying the exact cause.