VW Engine Performance & Diagnostics 2

Question 1

A 2.0T TSI shows long-term fuel trim at +18% at idle that drops to +3% at 3,000 rpm. What is the most likely cause?

Accepted Answer

An unmetered vacuum leak

Answer

A vacuum leak has the biggest effect at idle, when total airflow is low, and matters less as airflow rises.

Question 2

On a VW with a P0302 misfire, the technician swaps the cylinder 2 ignition coil with cylinder 3 and the code changes to P0303. What is the next step?

Accepted Answer

Replace the ignition coil that moved

Answer

The misfire followed the coil, so the coil is the faulty part.

Question 3

In VW component naming, what does G62 refer to?

Accepted Answer

Coolant temperature sensor

Answer

G62 is VW's designation for the engine coolant temperature sensor.

Question 4

Why are VW direct-injection (TSI/FSI) engines prone to carbon buildup on the intake valves?

Accepted Answer

Fuel is sprayed into the cylinder, so it never washes the backs of the intake valves

Answer

Port injection washes the valves with fuel, but direct injection skips the intake port, so oil vapor deposits build up.

Question 5

A leak-down test on one cylinder shows air escaping from the oil filler neck. What does this indicate?

Accepted Answer

Worn piston rings or cylinder wall

Answer

Air reaching the crankcase means it is getting past the piston rings.

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