I have an 01 Sable with the Duratec 3.0. I bought the car with 39000 miles and it has 143000 on it now. Happy with the car except in the winter. For the past 3 years when the temperature drops below 30 degrees, the car starts idling rough. The colder it gets the worse it idles. The idle jumps way up on the initial startup, and drops down and lopes really bad. It acts like its loading up with fuel. You can't seem to hold the rpms steady with your foot unless it's above 1500. After about 10 minutes or so, it will straighten up and you are fine until the next morning. I've replaced the pcv valve, I've replaced one split vacuum hose, i've replaced a coil pack, i've replaced the plugs, wires, coolant temp sensor, i've cleaned the maf sensor, i've also replaced the upper intake gaskets. I'm at a loss here. The codes that are coming up are a lean bank 2 code and a misfire bank 2 code. This is becoming a slow process because I fix one thing then have to wait until the next morning for the engine to be completely cold before firing it up and testing it again. I even went as far as taking off the air cleaner housing and forcing hot air in it with a hair dryer trying to trick the computer into thinking it was warm outside and the car quit running on me. I unhooked the MAF sensor connector while the car was idling and it didn't change nothing. It never even set a code when I unhooked it????? Please help,, summers coming and I want this fixed. I tryed on a Mercury Forum but couldn't get a response. Thanks.

 

This is what it sounds like to me, and I could be wrong.
When cold the ECM is programed to run on a few inputs, but has little control of fuel management. When warmed up , the ECM is able to compensate for the problem, if it is working properly.
The fact that no code was set when the MAF sensor was disconnected is something that needs to be checked further. Possible ECM or wiring.
Need to correct the obvious before you can go on.

 

I went out today and started the car. I unplugged the maf sensor and the check engine light did not come one. I shut the car off and left the maf sensor unhooked and started the car. The check engine light came on. It's just weird that it only does it while the car is warming up. I can't see a vacuum hose with a hole in it sealing itself back up. I can't see a sensor only working after it's warm. It may be the ECM. I'm not sure. I just would like to rule out all other possibilities first for cost reasons. Since it only does it when the outside air is cold I tryed tricking the computer into thinking that it was warmer by blowing hot air into the air filter box with a hair dryer and as soon as I did turn the hair dryer on the car quit. So I think the Maf is working. Dunno. Loss here. I am thinking it may be an upper intake gasket since I had it off changing plugs right before winter a few years ago. I need to take it back off and replace the gaskets and torque it with an Inch Pounds torque wrench. I dont have an Inch Pound torque wrence so I just tightened up by hand. I may have it to tight and It may be to loose.

 

Its worth a try.

 

I had the same problem with my 2001 Taurus DOHC. With 220,000 miles, I swapped everything with my 2001 DOHC Sable to try and figure out the problem. Last weekend, I decided to swap the fuel injectors. They are easy to work on - - I relieved the pressure, disconnected the line and then removed the 8 long bolts that held the two plastic lower intake manifolds to the heads. The rail, injectors and lower manifolds remove as one assembly. I placed the assembly from the Sable to the Taurus and all is well now - - even in these 0 degree mornings we had here the last couple of days. I ended up buying all new injectors ($30 a piece) for the Taurus BUT I think the problem was actually the lower intake gaskets. They are a rubber like O ring but they were really mashed flat - - I really think air was getting thru there when the engine was cold and then expanded enough to seal the vacuum leak when the motor warmed up. I would try changing those - - the new gasket set is only $17 at the autparts store and it is easy to do.