RSQ3 Power Loss & Jerking Due to Fuel System Issues

Had the same symptoms on my RS4 (2011, gasoline) last winter. The check engine light was constant and the engine showed identical behavior, rough idle, power loss, and jerking during acceleration. After diagnosis, it turned out the fuel injectors were failing, causing an inconsistent rich mixture. The mass airflow sensor readings were all over the place because of the uneven fuel spray pattern. The issue required replacing two faulty injectors and cleaning the remaining ones. This is definitely a serious problem that needs immediate attention since bad injectors can: Damage the catalytic converter due to unburned fuel, Cause spark plug fouling from excess fuel, Lead to complete engine failure if left untreated The diagnosis process involved: 1. Running injector pulse tests 2. Checking fuel pressure 3. Testing injector spray patterns 4. Scanning for specific fault codes Recommend having it properly diagnosed with specialized diagnostic equipment. A reputable shop should be able to identify which injectors are faulty through proper testing. This isnt a job for basic scan tools or guesswork, as misdiagnosis can lead to replacing wrong parts.

Thanks for sharing your experience with the RS4 injector problems. Your symptoms match mine exactly, including the erratic check engine light and rough running. Really helpful to know about those injector tests since the throttle body and oxygen sensor readings can be misleading with these symptoms. Did you remember roughly how much the repair ended up costing? Also curious if youve had any related fuel system issues pop up since getting it fixed? My local shop quoted a pretty high diagnostic fee just to start looking at it, so trying to gather some real world costs before proceeding.

After getting the RSQ3 properly diagnosed, it turned out you were right about the fuel mixture being the core issue. The mechanic found a defective injection valve that was causing those exact symptoms, rough idle, power loss and inconsistent performance. The repair cost came to 515 Euro which included: Complete injector diagnosis, Replacement of the faulty injector, System cleaning and calibration, New seals and gaskets Since fixing the bad injector, the mass airflow sensor readings have stabilized and the engine runs perfectly smooth again. No more check engine lights or rough running issues in the past few months. The intake manifold pressure is now steady and the fuel trim values are back to normal ranges. Getting that thorough diagnostic was worth it, even though the initial fee seemed high. A proper diagnosis prevented replacing unnecessary parts like the throttle body or spark plugs when the real problem was just that one faulty injector causing the mixture preparation errors.

Thanks for the detailed feedback. Finally got my RSQ3 fixed last week and wanted to share how it went. Ended up paying 580 Euro for the full repair after finding a reputable shop that specializes in fuel system diagnostics. The mass airflow sensor was reading inconsistently because of a failing injector, just like your case. They found carbon buildup in the intake manifold too, which was making the problem worse. The mechanic cleaned everything, replaced the bad injector, and did a full system calibration. Car runs perfectly now, no more jerking or power loss. The throttle response is smooth and the engine idles like new. Really glad I didnt waste money trying unusual fixes first. The proper diagnostic equipment made all the difference in pinpointing the exact issue. Worth every cent to have it done right. No check engine lights since the repair, and fuel economy has actually improved. Learned my lesson about getting proper diagnosis instead of guessing at the problem.