ADT Engine Performance & Tuning 2 — Questions and Answers
Question 1: On a 2019 Audi A4 2.0T, the ECU reports a lean condition at high load but fuel trims are normal at idle. Which component should you inspect first?
- High-pressure fuel pump (HPFP) (Correct answer)
- Mass airflow sensor
- Purge valve solenoid
- Intake manifold gasket
Correct answer: High-pressure fuel pump (HPFP)
The HPFP on TFSI engines commonly fails to maintain adequate rail pressure under high load, causing lean conditions that don't appear at idle.
Question 2: Audi's Valvelift System (AVS) switches between two cam profiles. Which symptom most commonly indicates a failed AVS solenoid?
- Rough idle and misfires at low RPM (Correct answer)
- Engine knock under heavy acceleration
- Oil consumption above 1 qt/1000 miles
- Coolant loss with no visible external leak
Correct answer: Rough idle and misfires at low RPM
A failed AVS solenoid prevents switching from the low-lift profile, causing rough idle and low-RPM misfires because the engine stays on the low-lift cam lobe.
Question 3: When performing a cylinder contribution test on an Audi 3.0T supercharged engine using ODIS, which parameter indicates a weak cylinder?
- RPM drop greater than 20 RPM when that cylinder is disabled (Correct answer)
- Fuel trim correction exceeding +10% for that cylinder
- Ignition advance retard of more than 4° on that cylinder
- Injector pulse width shorter than 1 ms on that cylinder
Correct answer: RPM drop greater than 20 RPM when that cylinder is disabled
During a cylinder contribution test, a healthy cylinder causes a significant RPM drop when disabled; less than 20 RPM drop indicates the cylinder is not contributing normally.
Question 4: A 2020 Audi SQ5 with the 3.0 TFSI exhibits a whistling noise that increases with engine load. The boost pressure reading is normal. What is the most likely cause?
- Cracked supercharger bypass valve housing (Correct answer)
- Faulty wastegate actuator
- Worn throttle body bore
- Clogged charge air cooler fins
Correct answer: Cracked supercharger bypass valve housing
A cracked supercharger bypass valve housing allows pressurized air to whistle through the crack under load while not significantly affecting overall boost readings.
Question 5: Audi's homogeneous-split injection mode combines port and direct injection. What is the primary purpose of this dual-injection strategy?
- To reduce intake valve carbon deposits while maintaining combustion efficiency (Correct answer)
- To increase peak power output beyond direct injection alone
- To lower exhaust gas temperatures during high-load operation
- To comply with OBD-II catalyst monitor readiness requirements
Correct answer: To reduce intake valve carbon deposits while maintaining combustion efficiency
Port injection washes the intake valves with fuel, preventing the carbon buildup inherent to direct injection only, while direct injection maintains efficiency.
Question 6: On an Audi with a timing chain tensioner fault, ODIS logs adaptation values for camshaft timing that are consistently at the negative limit. What does this indicate?
- The chain has stretched and the ECU is compensating by retarding cam timing (Correct answer)
- The VANOS solenoid is stuck in the fully advanced position
- The crankshaft position sensor has an offset error
- Excessive oil viscosity is preventing proper camshaft advance
Correct answer: The chain has stretched and the ECU is compensating by retarding cam timing
When cam adaptation values are at the negative limit, the ECU is maximally retarding the cam signal to compensate for a stretched chain that is advancing camshaft timing.
Question 7: During a DSG 7-speed DQ381 clutch adaptation in ODIS, the adaptation fails with error 'clutch contact point out of range.' What is the correct next step?
- Check mechatronic unit hydraulic pressure before repeating adaptation (Correct answer)
- Replace the dual-clutch pack assembly immediately
- Perform a throttle body adaptation first
- Flush and refill DSG fluid then repeat adaptation
Correct answer: Check mechatronic unit hydraulic pressure before repeating adaptation
Insufficient hydraulic pressure from a faulty mechatronic unit prevents accurate clutch contact point measurement, so verifying pressure is the correct diagnostic step before repeating adaptation.
ADT Engine Performance & Tuning 2
On a 2019 Audi A4 2.0T, the ECU reports a lean condition at high load but fuel trims are normal at idle.
Which component should you inspect first?