rainermoeller1
Rough Audi A3: Fuel Mix Issues Trigger Power Loss
Shaking while idling
Stalling while idling
Loss of engine power
Check engine light on
Jerking on acceleration
4 comment(s)
Last service was at 95270 KM, and after checking the air-fuel ratio issues carefully, I found my throttle body was heavily clogged with carbon deposits. A thorough cleaning of the throttle body resolved most symptoms, but I also discovered the mass airflow sensor was giving faulty readings. The fuel injection system started working properly once both components were addressed. For around 350 Euro, the repair shop cleaned the throttle body, replaced the mass airflow sensor, and recalibrated the system. The engine now runs smoothly without jerking or stalling. My spark plugs were also replaced as a preventive measure since they showed signs of carbon fouling from the rich mixture. Consider checking these components before diving into more complex repairs.
Thanks for the update on your A3. This matches my experience with VAG engines, cleaning the throttle body often resolves these rich mixture issues. When my check engine light came on with similar symptoms, I also discovered carbon buildup was the main culprit. Since you mentioned the spark plugs, that reminded me, after fixing my fuel injector, I had the same workshop do a full ignition system check. The carbon deposits from the rich mixture had indeed affected my spark plugs too. The mechanic showed me how the excess fuel had left dark, sooty deposits on them. One thing to keep monitoring is your oxygen sensor readings. Even with the new mass airflow sensor and clean throttle body, faulty O2 sensors can cause similar symptoms to return. Mine started acting up about 6 months after the initial repair, throwing off the air-fuel mixture again. Good to hear you got it sorted for 350 Euro, thats a fair price for the work done. Just remember to keep an eye on the catalytic converter health, as running rich for extended periods can damage it. Might be worth having it checked during your next service interval.
Thanks for sharing the comprehensive repair advice. The faulty mass airflow sensor and clogged throttle body diagnosis makes perfect sense. The rough running and stalling were clear indicators of air-fuel mixture problems. After getting the throttle body cleaned and replacing the mass airflow sensor for 350 Euro, my fuel injection system is working normally again. The carbon deposits were much worse than expected, which explains why the engine was running so rich. The shop also found my spark plugs were fouled from the improper mixture. Getting those replaced was a smart preventive step. Since the repair, there is no more jerking during acceleration or stalling at idle. For others facing similar issues: check these components before assuming more serious problems. A clogged throttle body and faulty mass airflow sensor can mimic many other expensive issues. The oxygen sensor readings are now stable, proving it was indeed an air measurement problem rather than a fuel system fault. Monitoring my catalytic converter health going forward, but so far the engine is running perfectly with proper fuel injection and air readings.
I had very similar symptoms with my Audi A4 2.0 (2004), and I have some experience working on VAG engines. The symptoms you describe match exactly what I dealt with, rough running, power loss, and the check engine light coming on. After initial diagnosis, it turned out the rich mixture was caused by a faulty fuel injector that was flooding one cylinder. The mass airflow sensor readings were normal, and the throttle body was clean. The workshop did a complete injector test which showed one injector was stuck partially open, causing too much fuel to enter the cylinder. The fix involved replacing the faulty injector and doing a full system reset. Total cost was 515 Euro including parts and labor. The car has been running perfectly since then. To help diagnose your specific case, could you share: Any diagnostic codes from the check engine light? Does the problem get worse when the engine is warm or cold? Have you noticed increased fuel consumption? Are there any unusual exhaust smells? Has the catalytic converter been checked? This information would help determine if your issue is similar to what I experienced with the injector.