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Experiencing Rough Idling and Misfires in my 2016 Audi Q5 2.0T - Carbon Buildup?

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Mark S. · rep 0 · May 25, 3:16 AM · 1 replies · solved · Question

Vehicle: 2016 Audi Q5 2.0T Premium Plus

Hey everyone,

I've been noticing some pretty rough idling lately in my 2016 Audi Q5 2.0T Premium Plus. It feels like the engine is struggling, especially when cold, and I've even had the check engine light come on a couple of times. When I scanned it, I got codes like P0301 and P0303, indicating misfires on cylinders 1 and 3.

I've heard that carbon buildup is a common issue with these direct-injection TFSI engines. Could this be the culprit? My Q5 has about 85,000 miles on it now, and I'm not sure if the previous owner ever had a carbon cleaning done.

What are the typical symptoms of severe carbon buildup, and what's the recommended maintenance or repair for this? Any advice on how to confirm if this is the problem before I take it to a specialist?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 3:16 AM

0

ClearTheCode admin answer:

It sounds like you're on the right track with suspecting carbon buildup, Mark. This is indeed a very common issue with Audi's direct-injection TFSI engines, especially as they accumulate mileage.

  1. Understanding the Cause: Direct injection engines spray fuel directly into the combustion chamber, bypassing the intake valves. This means there's no fuel 'washing' the back of the intake valves, allowing oil vapors and exhaust gases from the PCV system to deposit carbon over time. This buildup restricts airflow and can lead to misfires, reduced power, and poor fuel economy.

  2. Common Symptoms: Beyond rough idling and misfires (P0300, P0301-P0304), you might also experience:

    • Hesitation or a lack of power during acceleration.
    • Reduced fuel efficiency.
    • Engine knocking or pinging.
    • A persistent check engine light.

  3. Diagnosis: The most definitive way to diagnose severe carbon buildup is through a visual inspection of the intake valves. A mechanic can do this using a borescope inserted through the intake manifold. Some shops may also perform a compression test or leak-down test, as carbon buildup can sometimes affect valve sealing.

  4. Recommended Solution: The most effective solution is a walnut blasting service. This involves removing the intake manifold and using specialized equipment to blast finely crushed walnut shells at the intake valves. The walnut shells are abrasive enough to remove carbon but soft enough not to damage the metal. Chemical cleaners are generally less effective for severe buildup.

  5. When to See a Shop: Given the misfire codes and rough idling, it's advisable to have your Q5 inspected by an Audi specialist soon. Continued driving with significant carbon buildup can put added stress on other engine components and potentially lead to more costly repairs down the line. A professional can confirm the issue and perform the necessary cleaning.

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