Audi S5 Rough Idle and Sluggish Acceleration Fix Guide

I dealt with nearly identical symptoms on my 2019 Audi S4. The check engine light came on, accompanied by rough idling and jerky acceleration. The diagnostic scan revealed a faulty fuel injector in cylinder 2, which was causing an improper air-fuel ratio. The repair involved: Complete injector removal and testing, Replacement of 2 defective injectors, Cleaning the remaining injectors, ECU reset and adaptation This was a serious issue requiring immediate attention, as bad injectors can: Cause catalytic converter damage, Lead to cylinder misfires, Create excessive carbon buildup, Trigger oxygen sensor issues The repair took 2 full days at the shop. Its important to address injector problems quickly because running lean can damage other engine components. The EGR valve and intake manifold needed inspection too, as carbon deposits often accumulate when injectors malfunction. After the repair, the engine ran smoothly again with proper throttle response and consistent idle. These symptoms definitely point toward fuel delivery issues, worth getting it checked soon before secondary problems develop.

Thanks for sharing your experience with the S4 injector problems. My symptoms match yours exactly, the rough idle and jerky acceleration were driving me crazy. I got it sorted last month with similar repairs to what you described. The check engine light was definitely a wake-up call. Have your fuel injectors been running fine since the fix? Also, mind sharing what the total repair cost was? Just curious if I paid too much at my shop since they also mentioned potential catalytic converter issues during the inspection.

Good to hear you got it fixed! Since my repair, the injectors have been working flawlessly, no more rough idle or acceleration issues. The mass air flow sensor readings confirm the engine is running at optimal air-fuel ratio now, which was the main concern when it was running too lean before. The total cost came to 515 Euro for the complete job, including parts and labor. This covered testing, replacing the faulty injector, and cleaning the fuel system. The throttle body response is much smoother now, and fuel economy has actually improved a bit. Your mechanic was right to check the catalytic converter during inspection, running lean can definitely cause damage there. Luckily, catching the bad injector early prevented any secondary issues with the cat or spark plugs in my case. Its been about 8 months since the repair, and everything is still running perfectly. These direct injection engines are quite sensitive to injector issues, but once properly fixed, they perform great.

Thanks for the helpful advice. After taking my S5 to the mechanic last week, they confirmed it was indeed the fuel injectors causing the issues. The inspection showed two failed injectors and heavy carbon buildup in the intake manifold. The repair included replacing all fuel injectors as a set, cleaning the intake system, and running diagnostics on the mass air flow sensor. They also checked the catalytic converter but fortunately found no damage there. Total bill came to 890 Euro, more than I hoped but worth it for the complete job. Car runs like new now, no more jerking or rough starts in the morning. The oxygen sensor readings are perfect and fuel economy has actually improved. Really glad I got it fixed before any serious engine damage occurred. The mechanic explained everything clearly and even showed me the old injectors, they were in pretty bad shape. Next time I notice any engine running lean symptoms, I will definitely get it checked right away rather than waiting. Lesson learned about preventive maintenance on these engines.