All winter long I have been struggling with my 02 XType 2.5 Auto with 70k.

The car always starts, no matter how cold (even -22 f here in Minnesota) the problem is that it wont fast idle long enough 1200-2500 rpms to let the motor warm up enough to sustain itself. It starts, fast idles at about 1000rpm for 30 seconds then drops down to like 400 rpms and starts to pop and miss; at times triggering the check engine with codes for misfires.

I have done the following:
New plugs about 5k ago
New IMT gaskets
New lower intake manifold gaskets
New coolant temp sensor
Throughly inspected every vacuum line by listening for hissing, visual inspecting the known trouble spots e.g pvc hoses, power brake booster hose etc. Also used brake cleaner and propane along all contact surfaces. No vacuum leaks found.

Once the car is warmed up it runs great all day no matter how cold it is. It only happens when it sits overnight when it's cold below 20f.

So many people are reporting the same issue that I beginning to think there is a design shortcoming in this engine or possibly the software problem that leads to this problem.

Any thoughts or suggestions.

 

What trouble codes are you getting? You should have replaced the upper manifold gaskets and clean the MAF sensor.

I was having a similar problem and couldn't pin point the leaks until I did a smoke test.

Put a sealed plastic bag in the air intake tube to block smoke from leaking out. Light a cigar. Then pull the brake booster hose out and blow a lot of smoke into it. Any leaks will show up...

On my car I saw small leaks from manifold and a huge leak from side of throttle body. After fixing these leaks, my car ran very good in the cold mornings and all my check engine lights cleared.

 

I also being in Minnesota got fed up with the poor winter performance (running rough when cold and really bad gas mileage.) of the car and shoved it in the garage and started driving my truck instead. I might bring it back out in spring or I'll just sell it and buy something else. No point in owning a V6 AWD car if you can't drive it in winter.

 

Boston, I would check the side of the throttle body for any vacuum leaks and then I would remove the intake and clean the throttle body really good with some throttle body cleaner. It may be just that the gum on the inside of the throttle body is causing the butterfly valve to stick shut, leading to the car going to a really low idle. You may want to also consider cleaning the MAF sensor. Sometimes it is this little stuff that can make a big difference.