Vehicle: 2010 Volkswagen Tiguan 4Motion (5N1), L4-2.0L Turbo (CCTA), Automatic Transmission/Transaxle

Mileage: 178,228

Problem: The owner said that her malfunction indicator light (MIL) was on and that the engine would hesitate and lose power for about five minutes when it was cold. Then it would run fine.

Case Details: The technician connected a scanner and found these diagnostic trouble codes (DTCs).

• P0300 – Random Misfire
• P0301 – Misfire Cylinder #1
• P0302 – Misfire Cylinder #2
• P0303 – Misfire Cylinder #3
• P0304 – Misfire Cylinder #4
• P0506 – Idle Air Control System RPM Lower Than Expected
• P0299 – Turbocharger/Supercharger Under-boost

He cleared all the DTCs and went on a test drive to see which ones came back. All the same DTCs returned during the test drive. After checking the usual problems that could cause multiple cylinder misfires, the tech called ALLDATA Tech-Assist.

The Tech-Assist consultant advised checking the crankcase vacuum. The reading should not be more than 2-3 in/Hg. He also advised checking the engine vacuum for a fluctuating needle, which may indicate carbon buildup on the intake valves. It’s a common issue with these motors.

The tech performed both vacuum tests as suggested and found the vacuum gauge needle shook a lot at idle when cold. He pulled the intake and found excessive carbon buildup on the valves.

Confirmed Repair: After cleaning the valves, the tech cleared the DTCs and took the Tiguan on a brisk road test. There were no further issues. Fixed!