S8 Engine Stalling & Smoking: Failed Injector Warning Signs

As an S6 owner with the same 4.0L power unit, I faced identical symptoms last year at 165000km. The main issue was a faulty fuel pressure sensor and damaged wiring to the injection control module. The system was losing proper fuel pressure regulation, causing both the excessive consumption and performance issues. The smoke under acceleration typically indicates the system running rich, pumping excess fuel through the combustion chambers. When combined with stalling at idle, this strongly suggests injection system faults rather than mechanical engine wear. Required repairs involved: Testing fuel pressure sensor operation, Replacing damaged wiring harness, Recalibrating injection timing, Full system diagnostic scan This was a critical maintenance issue requiring immediate attention, as continued operation risked damaging the catalytic converters and oxygen sensors. The injection system on these engines is quite complex but very reliable when properly maintained. Recommend finding a specialist familiar with Audi direct injection systems, as general repair shops often lack the diagnostic equipment needed for proper troubleshooting of these engines.

Thank you for sharing your experience with the S6 fuel system issues. My engine ended up having very similar symptoms. The smoke and power loss really had me worried. After getting it fixed, the engine runs perfectly again, with normal fuel consumption. Did you keep track of the total repair costs for the fuel pressure system? Also curious if you had any other issues pop up since having that fixed? My air filter was also quite clogged when they checked it, which apparently made the original problem worse due to the poor air-fuel mixture.

Had the pressure sensor and wiring issues fixed last month, total came to 95 Euro for repairing the faulty cable connection to the injection system. Pretty reasonable considering the symptoms. The repair has completely resolved the power loss and excess fuel consumption problems. The system has been running flawlessly since the fix, no other issues to report. Good observation about the air filter, these engines are sensitive to the air-fuel mix. I make sure to check mine regularly now to prevent similar problems. With the injection system working properly again, the engine response and fuel economy are back to normal. Getting it sorted by a specialist who actually understood the petrol direct injection setup made all the difference. While these engines can seem complex, most issues trace back to relatively simple electrical or sensor faults in the fuel delivery system.

Thanks for sharing that feedback. After getting over my hesitation, I took it to a specialized performance shop. They found the exact same issues you mentioned, faulty fuel pressure sensor and some damaged wiring. They also noticed the clogged air filter during inspection. The repair work was straightforward once properly diagnosed. All in it cost 850 Euro for parts and labor. Money well spent since the engine now runs beautifully again. No more smoke, stalling or performance problems. Fuel consumption is back to normal too. Learned my lesson about proper maintenance schedules and not ignoring small issues before they become bigger problems. The air system cleaning and new filter made a noticeable difference in how the engine runs. Regular checks of these systems really do help prevent more serious issues down the line.