To check and tighten speaker connections, start by turning off the car's audio system and disconnecting the power source. Carefully remove the speaker grille or panel to access the speaker and its connections. Inspect the connections for any loose or disconnected wires. If you find any loose connections, use a screwdriver or appropriate tool to tighten them securely. Ensure that the positive and negative terminals are properly connected to the corresponding terminals on the speaker. It is also important to check the connections at the amplifier end, as loose connections there can also cause distortion.