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2018 Q5 Excessive Oil Consumption & CEL - P0171 Possible PCV?

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Mike T. · rep 0 · May 25, 3:15 AM · 1 replies · solved · Question

Vehicle: 2018 Audi Q5 Premium Plus

Hey guys, I'm dealing with a frustrating issue on my 2018 Audi Q5 Premium Plus, 2.0T engine, with around 75,000 miles. For the past few months, I've noticed it's burning through oil much faster than usual – I have to add a quart every 1,500-2,000 miles. Recently, the Check Engine Light came on, and when I scanned it, I got a P0171 code (System Too Lean Bank 1).

I've read online that excessive oil consumption and a P0171 code can sometimes point to a failing PCV valve or oil separator on these 2.0T engines. Is this a common issue for my model year? What are the symptoms I should look for to confirm it's the PCV, and is this something a moderately skilled DIYer can tackle?

Any insights or diagnostic steps would be greatly appreciated before I dive in.

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 3:15 AM

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ClearTheCode admin answer:

Your symptoms – excessive oil consumption and a P0171 (System Too Lean Bank 1) diagnostic trouble code – are indeed highly indicative of a failing PCV (Positive Crankcase Ventilation) valve or oil separator on your 2018 Audi Q5 2.0T. This is a very common issue for the EA888 Gen 3 engine found in your vehicle.

Causes & Symptoms of a Failing PCV:

  1. Diaphragm Rupture: The internal diaphragm in the PCV valve can tear, leading to a vacuum leak. This unmetered air causes the engine to run lean (P0171).
  2. Oil Consumption: A faulty PCV can allow excessive oil vapor to be drawn into the intake manifold, where it's burned off, leading to increased oil consumption.
  3. Whistling/Sucking Noise: You might hear a high-pitched whistling or sucking sound from the engine bay, especially at idle, due to the vacuum leak.
  4. Rough Idle/Misfires: A significant vacuum leak can cause an unstable idle and potentially misfires.
  5. Oil Cap Test: While the engine is running, carefully try to remove the oil filler cap. If it's extremely difficult to remove due to strong vacuum, it's a strong indicator of a failed PCV valve.

Recommended Steps:

  1. Confirm Diagnosis: Perform the oil cap test. If there's excessive vacuum, the PCV is likely the culprit. You can also use a smoke machine to visually confirm vacuum leaks around the PCV assembly.
  2. PCV Valve Replacement: The PCV valve assembly is usually located on top of the engine. It's often a relatively straightforward DIY job for someone with moderate mechanical skills. You'll need basic hand tools and possibly a torque wrench.
    • Parts: Ensure you purchase a genuine Audi PCV valve or a high-quality OEM equivalent. Inferior aftermarket parts can fail prematurely.
    • Procedure: Disconnect necessary hoses and electrical connectors, unbolt the old PCV, clean the mounting surface, install the new PCV, and reassemble.
  3. Clear Codes: After replacement, clear the P0171 code with an OBD-II scanner.
  4. Monitor Oil Level: Continue to monitor your oil consumption closely after the replacement. It should significantly decrease or return to normal levels.

When to See a Shop:

  • If you're uncomfortable with the DIY procedure or lack the necessary tools.
  • If, after replacing the PCV, the P0171 code returns or the oil consumption persists, indicating a different underlying issue (e.g., piston rings, turbocharger issues).
  • If you notice other severe symptoms like excessive blue smoke from the exhaust, which could point to more serious engine wear.
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