Symptom Descriptions

Interfering Noises
There are many possible sources of radio interference:
^ One such source is the vehicle ignition system. This high-voltage switching system produces a radio frequency electromagnetic field that radiates at AM, FM and CB frequencies. Although components have been designed into the vehicle to minimize this concern, the noise is more noticeable if the radio chassis is tuned slightly off channel when listening to FM programs.
^ Vehicle electrical accessories and owner add-on accessories may also contribute to radio interference.
^ There are many noise sources outside the vehicle such as power lines, communication systems, ignition systems of other vehicles and neon signs.

Ignition Noise
The most effective method of evaluating ignition noise is to compare the radio chassis performance with the engine on, versus engine off. If ignition noise is present with engine running:
^ Check to see that the spark plug wires are the suppressor type and that the spark plugs are the correct resistor type.
^ Check to see that spark plug wires are fully seated in ignition coil towers.
^ Check to see that spark plug wires are fully seated on spark plugs.
^ Check to see that spark plugs are properly gapped and seated in cylinder heads.

Missing or Damaged Noise Suppression Components
^ Noise suppression components may be damaged or missing.
^ Check radio frequency interference suppression grounding effectiveness by wedging a large file between metal parts to make sure of proper ground, such as between the tail pipe and body or between the fender and frame, while radio chassis is playing and engine is running.
^ Listen for a decrease in the objectionable radio chassis noise. If a reduction in noise is noted, first try tightening body and exhaust system clamps and brackets. Then, if necessary, install a new radio frequency interference suppression bond between the two metal parts to make sure of proper ground.