Audi A6 C8: Flickering Check Engine Light and Rough Idle

If your Audi A6 C8 has a check engine light that flickers intermittently and the idle feels rough, you're right to pay attention. On this generation, that combination almost always means the engine is misfiring — one or more cylinders aren't burning fuel properly. The flicker is the ECU's way of saying the misfire is active and potentially damaging your catalytic converter. A steady light is less urgent; a flashing or flickering one is a red alert.

Likely causes to check first

Start with a full OBD-II scan, not just a generic code reader. You want stored and pending codes, freeze-frame data, and live misfire counters. Look for P0300–P0308 (random or cylinder-specific misfire), fuel trim codes, or lean/rich codes. On the C8 A6, the usual suspects are:

• Ignition coils and spark plugs — especially on 2.0 TFSI and 3.0 TFSI engines; coils can break down when hot and cause intermittent misfires.
• Fuel injectors — direct injection means carbon buildup and injector clogging are common; a faulty injector can cause a rough idle and a flashing CEL.
• Vacuum leaks — check the PCV valve, intake manifold gaskets, brake booster line, and boost hoses. A leak leans out the mixture and makes idle rough.
• Mass airflow (MAF) or manifold pressure (MAP) sensor — dirty or failing sensors send wrong fuel data.
• Oxygen sensors and fuel pressure — a weak low-pressure fuel pump or a failing high-pressure fuel pump can cause lean misfires.
• Diesel-specific issues — on 2.0 TDI and 3.0 TDI, check injector correction values, fuel filter, EGR valve, glow plugs, and swirl flaps.

Is it safe to keep driving?

If the check engine light is flashing or flickering and the idle is rough, my honest advice is: don't keep driving. An active misfire dumps unburned fuel into the exhaust, which can overheat and destroy the catalytic converter — a very expensive repair. Limp it to a safe spot, then have it towed or driven only to a nearby shop if absolutely necessary. If the light is steady and the car otherwise drives smoothly, you can carefully drive to a garage for diagnosis, but avoid hard acceleration and long trips. On a C8 A6, a proper diagnosis with live data will save you from throwing parts at it. Fix the root cause, clear the codes, and enjoy that smooth Audi idle again.

This material is AI-generated and for informational purposes only — it does not replace an in-person diagnosis by a qualified mechanic.