1998 - Diagnosing an intermittent problem

I have a '98 Mercury Sable (U Vin) and recently I have a hard time starting the car when it's hot. I've also had a problem starting it when cold. I tested the battery and it didn't do well under load, so I replaced it. It starts when it's cold now, no problem. Now when I drive anywhere and get the car up to normal operating temp, if I stop for a short period of time, say to pick up a six pack, when I come out of the store, sometimes it won't start. Other times, it starts fine. I've tested the Engine Temperasture Sensor (ETS) using a voltmeter, and when it's in my garage, I can not recreate the conditions to see if it is the ETS. It passes the ohm test listed in the Hayne's Manual. Any suggestions as to what I should be looking for, anything else I should test?

I've had a similiar experience with my 97 sable wagon GS, same U in Vin not sure if its the same engine type tho.

Old battery died, had the same probs, Installed a new battery.

I changed out the Heater Thermostat, (not sure if thats the correct name), the valve wasnt working, part was 8 bucks. But has had the same symtoms your describing.

Altho I had to also change out the Sparkplugs/wires/distcap for it while I did change out the thermostat.

Not sure if yours is the same. Hopes it helps you.

But now I dont have the problems your describing either.

I did this change out on Oct 18, 2005.

Do you mean the thermostat that's in the housing conected to the lower intake manifold? This housing is right next to the Engine Coolant Temperature Sensor which I replaced Friday. I did all of the wires and plugs in June.