What can cause the temperature gauge to malfunction? It is a 5.7L engine.

There are no lights or codes. I have had to replace the plugs, wires, distributor cap, rotor, and ignition coil. Also had to replace oil cooler lines and radiator. It was in rpugh shape when I got it.

Best to use a scanner to 'test' the actual engine temperature as seen by the computer and compare it to temperature guage reading .. Possible guage malfunction .. Thermostat partially stuck open .. Or inaccurate temperature sensor reading . .. 'Some' code readers have the live data feature and can be used for this .. However a real (pro quality) scan tool can actually test the instrument cluster gauges using functional test.

I will look into that. Thank you for your help