I have a 93 lx 2.3L. 43k miles. I have flused and back flushed system. Replaced water pump, thermostat, temp sensor, lower hose and radiator cap. Coolant temp will reach normal when sitting at idle. Soon as I start driving it. It drops down to 130. Seems to go into limp mode. Code I got off jumping the port was 21 (coolant temperature out of range). I can't figure this out. Can anyone help??