It's slightly cool in fla lately but the car has been doing it even when it's warm outside. The engine temp only goes to normal operating temp at idle. When I start driving it goes all the way to just above cold, when its cold outside it goes allllllllll the way to cold. The problem is it keeps thinking I just started the car and the cold start idle kicks in. So I'll drive 5 miles on the highway and get off, stop at a light and my car is idling at 1500-1700 rpms. The heater core by-pass has been done to the car..... Not really sure if that makes a difference. Can anyone help to diagnose this?

 

Sounds like you have something stuck in your theromostat or it is stuck open. I used to have the same problem, but only in the winter time here in TX. But then I was changing the thermostat & found a piece of black silicone stuck in the thermostat. So check that.

 

I don't have a heater either but mine doesn't do that. Once it gets half way, it stays like that. It could be a thermostat stuck open or maybe even the sensor is going back.

 

^ agreed thermostat sounds like its stuck open or possibly no thermostat installed?

 

My thoughts exactly...I'm banking on no thermostat and just water and not coolant. or maybe the wrong ratio, water cools better and faster, and takes a lil longer to heat up . But boils much much faster...