Whistle at idle, slightly rough idle and a lean code
2012 · Volkswagen Passat B7 · 1.8 TSI (CDAB) · 136,000 km
P0171
Root cause: Split diaphragm in the crankcase breather (PCV) valve, letting in unmetered air and losing crankcase pressure control.
Case library
Share a caseReal faults, real fixes
Repair cases shared by mechanics and reviewed before publishing. Hide the solutions to diagnose them yourself first. Cases marked "Training case" are written by ipacen from typical faults for practice.
Rattle for two seconds on a cold start, then a warning light
2011 · Volkswagen Polo V · 1.2 TSI (CBZB) · 88,000 km
P0016
Root cause: Timing chain stretched and its guide worn, so the tensioner could no longer take up the slack on cold starts.
Long crank when warm and white smoke for a few seconds
2011 · Volkswagen Golf VI · 1.6 TDI (CAYC) · 178,000 km
P0266
Root cause: Injector no. 2 worn internally: too much leak-back while running and dripping into the cylinder after shut-off.