1999 Mercury Villager won't run when warms up

Ok yes we can test it. I also need to know what size engine is in it and if you have a digital multi meter. Also is the check engine light on? If so can you get a scanner to use to see what the car is telling us? Get back to me with as much info as you can and we will go from there. Thanks.

Engine light is not on. It is a 3.3L V6.

I have a multi meter unit.

Ok I need you to test the coolant temp sensor first. All you need to do is unplug it and check the ohm's across the sensor (not the harness) and do this cold so you can tell me what the abiant air temp is too. Then if that tests ok then we will go to testing the Module. Now if the module is bad it only comes as a whole distributor. You have checked the cap and rotor and ohmed out the plug wires. Any way one thing at a time. Lets test the coolant temp sensor first and go from there.

Sensor measures 4k ohms at approx 40 degrees. Wiring checks our okay.

this morning it started and ran fine while cold. I had reconnected the sensor and the engine light came on. I ran the engine until it was warm and disconnected the sensor. No effect. I turned off the engine and measure for ohms on the sensor; almost zero at about 170 degrees. What's next?

Ok that sensor is definetly bad. It should be be .9 ohms at 194 degrees so it is out of range. Now this may not be the total fix but with it bad it is hard to do more tests and be acurate. So replace that sensor and go to your local parts store (one that does a free scan) and scan you car and again write down the codes and then have them clear the codes. While there if you would pick up some mass air flow cleaner and remove and clean the mass air flow unit. Do not use anything other then mass air flow cleaner on it ok. The mass air flow sensor looks like this so this is what you will remove and clean ok.