A 1998 V6 Mustang may experience several common problems over time. Some of the most frequent issues can be:

1. Engine Misfire - This can occur due to a faulty fuel injector, spark plug, or ignition coil, and may cause the engine to run rough or hesitate.

2. Faulty Transmission - Older vehicles' transmissions may shift harshly or fail to shift altogether, causing issues with acceleration and speed.

3. Leaking Radiator - A damaged or leaking radiator can cause overheating, which can lead to serious engine damage, and may need to be replaced.

4. Suspension Problems - Worn out bushings, ball joints, or tie rods can cause steering issues and make steering difficult.

5. Electrical Issues - The electrical system may have problems with the alternator, starter motor or battery, which can cause your vehicle to fail to start or other electrically-related issues.

It is necessary to have these issues inspected by a professional mechanic to determine the cause of the problem to prevent any further damage or expensive repairs.