Audi 80 Quiz
MPI and MPFI Injection Systems

CO Content Out of Specification

In this manual: MPI and MPFI Injection Systems
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
~1min read

If the CO content is out of specification, look mainly for leaks in the air intake and exhaust system. Next, make sure the ignition system is in good order (a faulty spark plug increases CO content by 1.5 %).


CO content too high:

Check the fuel injectors.

Fuel pressure too high.

Coolant temperature sensor faulty.

CO content too low:

Unmetered air is entering the air intake system.

Note: all information on the CO test, catalytic converter function check, lambda sensor check and throttle cable can be found in the chapter "Mono-Motronic Fuel Injection System".

Disconnecting the battery erases the idle speed correction factor of the fuel injection system. The system must therefore slowly re-learn the correct idle speed, which takes several minutes. Do not panic if the vehicle runs slightly unevenly after the battery has been replaced; simply drive for a short time until the adjustment is complete.

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