Coolant Temp sensor.

Okay so my Jeep died on me last week and so far every thing has been okay since. The only difference that I have noticed is when I start the Jeep after sitting for a while, like overnight or at work all day, it is harder to start now. It cranks for a while before it fires. I also noticed that Automaticly once it starts the coolant temp is right above 100* in 35* weather. Is there a problem I should be looking into?

temp sending unit, you are getting bad info on your gauge. there may also be a short in the gauge/sender wiring causing this misinformation. you know it's not 100* when you first start it...

On a 99 there is only one sensor, if your screen name is any indication. On my 98, the wiring harness got pinched between the firewall and the fuel rail, leading to worn through grounding out wires. This made my temp guage jump from normal to maxed out whenever I put it into reverse.

Check your sensor (it's in the thermostat/waterpump housing) and check your wiring back to the ECU.

And CEL codes?

The only code I ever get is for the 2nd o2 sensor. I know I need to get that replaced. This morning when I started the jeep it was not above 100*, but when I started it at 5:00 after work in 70* weather it read just above 100*. Would the hard starting have anything to do with the fuel pump?