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P0420

2018 Volkswagen Golf

Volkswagen

Severity

Medium

Safe to Drive

Yes

Est. Time

3hrs

Difficulty

Moderate

SYMPTOM

Check engine light, mild rough idle

Why This Happens

VW's direct-injection engines lack fuel washing over the intake valves, making carbon buildup a uniquely common upstream cause that indirectly loads the catalytic converter.

VERIFIED FIX:

Intake valve carbon cleaning

How It Was Diagnosed

VW's direct-injection engines lack fuel washing over the intake valves, making carbon buildup a uniquely common upstream cause that indirectly loads the catalytic converter.

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