Whenever I start my car, the temperature gage jumps all the way to the right (see the upper left-hand gage in the picture). Then after about 45 minutes of running the car, the temperature gage returns to a normal level with the needle in the middle of the gauge. Is this due to the temperature sending unit? I'd really appreciate people's thoughts on what might be the root cause. Thanks!
Try this - its free and even though it is primarily for 5.0 fox bodied cars, it may help you fix your problem.
The secondary power ground is between the back of the intake manifold and the driver's side firewall. It is often missing or loose. It supplies ground for the alternator, A/C compressor clutch and other electrical accessories such as the gauges. The clue to a bad ground here is that the temp gauge goes up as you add electrical load such as heater, lights and A/C. Make sure that the ground places are clean and shiny bare metal: no paint, no corrosion.