Interference noises due to engine

The following points should be checked first:

NOTE:

Make sure that the battery connections are seated properly and that the ground connection is guaranteed.
Check whether the ignition coils are loose or defective.
Check the plug connections and supply lines for the ignition coils for damage.
Check the ground connections on the engine.
Check whether the correct spark plugs have been installed and that the electrode gap is OK.

RADIO SYSTEM DIAGNOSIS FOR INTERFERENCE NOISES DUE TO ENGINE

Work instruction		Yes	No
1	Does the interference noise change with the engine speed? This work instruction must not be carried out on public roads.	Drive the vehicle in 1st or 2nd gear at a speed of 3,000 rpm (with audible noise), then suddenly remove the pressure from the accelerator. Noise present: Check the lead connections to the injection nozzle. Check in particular for loose or corroded connections. Check resistance of the injection nozzles. R = 12 Ohm +/- 0.6 ohm. Noise no longer present End Noise present Check the points listed above under Note once more.	Does the interference noise only occur when the car is driving? Step 2 Does the noise not occur when the car is driving? Step 3
2	Check for faults caused by vehicle components which have an influence on the speed. Disconnect the component from the power supply and test again. Noise still present?	Check the wiring of the components for unfavourable positioning and loose or corroded connections. Lay the cables again or repair. As an experiment, insert a functional component and replace, if necessary. End	Check the radio reception End
3	Check the wiring of the components for unfavourable positioning and loose or corroded connections. Lay the leads again or repair. Noise still present?	As an experiment, insert a functional component and replace, if necessary End	End