[Z U L8R]

coolant temp sensor for the ecu is 2 wire. it lets the ecu know whether the motor is hot or cold so it can adjust it's fuel trim accordingly.

when your motor is cold the intake manifold and intake valves are cold, therefore in order for the motor to atomize the fuel at the same programmed air fuel ratio it must dump a lot more in order to keep that same air fuel ratio. when the motor's warmed up it can atomize the fuel better therefore less fuel is needed.

when a car exhibits drivability symptoms based on it's temperature, this is one of the first things that is checked because on a fuel injected car A LOT of how the ecu will control the fuel trim and timing is based on the signal it gets from the coolant temp sensor.

not to be confused with the coolant temp sender, coolant temp sending unit, or coolant temp switch. all 3 are the same thing, different places call them different things however just like any sending unit it is a reference for the GUAGE. just like an oil pressure sending unit is for the guage. most cars have a coolant temp sensor for the ecu and a coolant temp sending unit for the guage, such as your car. however some newer cars use the same coolant temp sensor the ecu uses in order to work it's guage, therefore it's 2 in 1. this is a moot point since this does not apply to you.

whatever your guage has been saying has nothing to do with what the ecu is seeing. typically when a coolant temp sensor goes bad it will tell the ecu that it's -40 degrees and therefore the ecu will dump fuel, whether the motor's cold or hot since it's getting this incorrect signal the ecu has no way of knowing. it's going to do what it's programmed to do based on the feedback it gets from it's sensors. in that scenario the symptoms will be the car runs fine until it warms up.

however not every time a coolant temp sensor fails will it be a completely open circuit and give no feedback like the first scenario. sometimes it will go on the other end of the spectrum and the car runs like crap until it gets warm. it'll be hard to start, and exhibit more of the symptoms your car has.

being that this is such a cheap sensor to buy and replace, as well as a very common thing to go bad on these vehicles, naturally it is my first suggestion since your car is not here in front of me to see more obvious things that may have been overlooked.

typically people won't make a thread unless they've exhausted all resources and checked everything they know how.

if you'd rather fumble in the dark or spend money replacing more expensive things, then that's fine.

if you've already exhausted all resources and would like to try a $16 dollar sensor that may fix your problem, i'd agree with you.

if it's been a while since it's had a good tune up then that wouldn't hurt either.

best of luck,

Dave