ADT ADT Fuel System & Injection Technology 2 — Questions and Answers
Question 1: A 'fuel trim' value of +25% on a long-term fuel trim (LTFT) reading on an Audi TFSI indicates:
- The ECM is adding significant fuel, suggesting a lean condition (vacuum leak, low fuel pressure, or faulty MAF) (Correct answer)
- The system is running rich and removing fuel
- Normal operating range
- A faulty oxygen sensor with no further action needed
Correct answer: The ECM is adding significant fuel, suggesting a lean condition (vacuum leak, low fuel pressure, or faulty MAF)
+25% LTFT means the ECM is compensating heavily for a lean condition by adding extra fuel, indicating a significant air leak or fuel delivery deficiency.
Question 2: What special tool is required to correctly time the high-pressure fuel pump camshaft lobe on an Audi 2.0 TFSI engine during installation?
- Camshaft locking/alignment tool set specific to the EA888 engine (Correct answer)
- Universal valve spring compressor
- Standard timing light
- Generic harmonic balancer puller
Correct answer: Camshaft locking/alignment tool set specific to the EA888 engine
Audi EA888 engines require a specific camshaft locking tool set to correctly position the cam lobe for high-pressure pump installation and prevent engine damage.
Question 3: Which fuel system component on Audi direct injection engines is responsible for regulating high-side rail pressure by controlling the amount of fuel the high-pressure pump displaces per stroke?
- Fuel Pressure Regulator Valve (N276) on the high-pressure pump (Correct answer)
- In-tank fuel level sender
- Low-pressure fuel pump check valve
- Fuel rail pressure relief valve only
Correct answer: Fuel Pressure Regulator Valve (N276) on the high-pressure pump
The N276 solenoid valve on the high-pressure pump modulates fuel displacement per stroke to maintain the target rail pressure commanded by the ECM.
Question 4: A technician suspects a leaking high-pressure fuel injector on an Audi 3.0 TFSI. The BEST method to confirm this without disassembly is:
- Monitor individual cylinder fuel trim imbalance data with a scan tool and perform a static leak test (Correct answer)
- Smell the exhaust for fuel odor only
- Inspect the injector wiring harness visually
- Replace all six injectors simultaneously
Correct answer: Monitor individual cylinder fuel trim imbalance data with a scan tool and perform a static leak test
Cylinder-specific fuel trim data reveals imbalances that indicate a leaking injector, and a static leak test confirms internal leakage without disassembly.
Question 5: On Audi vehicles, the fuel tank pressure sensor is used primarily in conjunction with which system?
- Evaporative Emissions (EVAP) system leak detection (Correct answer)
- Direct injection pressure control
- Turbocharger wastegate control
- EGR valve positioning
Correct answer: Evaporative Emissions (EVAP) system leak detection
The fuel tank pressure sensor monitors tank pressure changes to detect EVAP system leaks as part of the onboard leak detection routine.
Question 6: What is the recommended Audi service action when carbon deposits on intake valves are confirmed on an EA888 TFSI engine?
- Walnut shell blasting of the intake ports while valves are closed (Correct answer)
- Chemical fuel additive treatment only
- Intake manifold replacement
- Throttle body cleaning with solvent spray
Correct answer: Walnut shell blasting of the intake ports while valves are closed
Walnut shell blasting through the intake ports is Audi's recommended procedure to mechanically remove hard carbon deposits from intake valves without engine disassembly.
ADT ADT Fuel System & Injection Technology 2
A 'fuel trim' value of +25% on a long-term fuel trim (LTFT) reading on an Audi TFSI indicates: