Audi 80 Quiz
Mono-Motronic Injection System

Fault Table - Mono-Motronic Injection System

In this manual: Mono-Motronic Injection System
Technical Description — 39Engines — 41Exhaust System — 13Cooling System — 28Fuel tank and fuel pump — 12Air Filter and Intake Ducts — 13Mono-Motronic Injection System — 18Digifant Injection System — 19KE-III-Jetronic Injection System — 35MPI and MPFI Injection Systems — 32Clutch — 11Transmission and Driveline — 21Suspension and Steering — 33Brake System — 41Anti-lock brake system — 8Wheels and Tires — 13Body Electrical System — 35Ignition System — 24Lighting — 14Signaling Devices — 7Instruments and Auxiliary Equipment — 54Heating and Ventilation — 7Body Components — 18Troubleshooting — 6Specifications — 13
~2min read

If you do not have the option of reading the fault memory with the Audi workshop tester, you can try to locate the fault using our fault table.

Malfunction Possible Cause Remedy
A. Cold engine does not start at all or starts with great difficulty 1. Faulty fuse 13, 21, 25, 27 or 28
2. Faulty wiring of the injector additional resistor
3. Fuel pump does not deliver fuel at all or delivers very little
4. Faulty fuel pressure regulator
5. Faulty coolant temperature sensor
6. Faulty throttle valve potentiometer
7. Faulty control unit
8. Faulty wiring harness between Hall sensor and control unit
9. Unmetered air entering the engine		 Replace
Check, replace if necessary

Is there any fuel in the fuel tank at all?
Check the pump, measure the fuel delivery quantity
Measure fuel pressure (at a workshop)

Check at a workshop

Check at a workshop
Check cable continuity
Perform a visual check as described in the instructions
B. Warm engine does not start at all or starts with difficulty 1. See A 2 – 9
2. Injector is leaking		 Check the injector
C. Engine starts but stalls again 1. Throttle valve actuator not working
2. See A6
3. Defective lambda sensor		 Check the actuator
Check operation, replace if necessary
D. Cold engine shakes at idle 1. See A 5
2. See C 1
E. Warm engine shakes at idle See C1
F. Idle speed drops when high-power consumers are switched on or when the power steering is turned fully See C1
G. Engine runs unevenly 1. Clogged fuel filter
2. See A3
3. See B2
4. See C3		 Replace the filter
H. Fluctuating engine speed at 2000–3000 rpm See A6
I. Engine runs unevenly and stalls See A3
J. Insufficient engine power 1. See A3, 6 and 9
2. See C3
4. Throttle valve does not reach full throttle position
K. Backfiring in the intake manifold 1. See A4
2. See C3
L. Fuel consumption too high 1. See A5 and 6
2. See C3

Note: Disconnecting the battery erases the adaptation values of the Mono-Motronic injection system. As a result, after power is restored, the engine may run unevenly at idle for some time. The adaptation values recover fastest during a drive of approximately 10 minutes.

Test yourself

A quick Audi 80 quiz: every answer comes with an explanation and a link to the manual page.