"Because your vehicle’s engine is electronically controlled by a computer,
some control conditions are maintained by power from the battery. When
the battery is disconnected or a new battery is installed, the engine must
relearn its idle and fuel trim strategy for optimum driveability and
performance. To begin this process:
1. With the vehicle at a complete stop, set the parking brake.
2. Put the gearshift in P (Park) (automatic transmission) or the neutral
position (manual transmission), turn off all accessories and start the
engine.
3. Run the engine until it reaches normal operating temperature.
4. Allow the engine to idle for at least one minute.
5. Turn the A/C on and allow the engine to idle for at least one minute.
6. Drive the vehicle to complete the relearning process.
• The vehicle may need to be driven 10 miles (16 km) or more to
relearn the idle and fuel trim strategy.
• If you do not allow the engine to relearn its idle trim, the idle
quality of your vehicle may be adversely affected until the idle
trim is eventually relearned."

 

Sounds like a bad IAC. Maybe just doesn't like the cold weather. Fuel filter shouldn't be the problem as the vehicle is OK at speed.

 

The OP stated in his second post that it begins after the engine warms up suggesting it's starting after the engine goes from open to closed loop (or is it closed to open?... Damned aging thing). IMO, that might rule out the fuel filter and point more towards controls. I still wouldn't rule out the TB.

 

Had the same problem a year ago. Mine actually went into limp home mode. Took it to the dealership and they ended up replacing the throttle body because it was 'sticking'. Mine is not stock, and I was running a mileage tune at the time. It started to happen again this fall, so I switched up to the performance tune and didn't have any more trouble this fall. I plan on switching back to the mileage tune and trouble shooting in the spring.

 

Thanks for all the replies. I am going to start work on it tonight. I made it home, but it was doing a different thing for the drive home. It was no longer dieing at at stops but every now and then while at speed, it would have a pretty good stumble. The check engine light came on this time, but I didn't have a chance to read the code yet.

I'll post my results either late today or tomorrow. Thanks again for the suggestions!

 

Thanks for the update! Hope you are able to get it worked out soon!

 

MAF Cleaned, TB cleaned, Fuel Filter replaced. Going for a drive shortly.

When I pulled the fuel filter, the gas that ran back out the input side was a very, very dark brown, almost black. Hopefully the fuel filter will solve the problem.

 

First 15 min test drive went great! Now for the morning commute tomorrow!

Thanks again for the all the help!

 

Maybe I missed it, but how many miles are on the car and on that old fuel filter? I changed mine at about 32,000 miles and the fuel that came out of it was tinged brown but not too bad. I've heard others state a very wide range of "clean" to "dirty dark brown", too.

Let us know how she's doing.

 

Car ran great on the commute in, seems like a bit more power than she had lately and the gas mileage on the computer was running about 1 mpg higher than I've been getting lately.

The fuel filter had a good 40k miles on it, 65k on the car.

I'm thinking the problem is solved, and now that I've played with the mustang a bit I think I've been bitten. I have visions of a cold air intake and new throttle body in my future...

Thanks again for all the help!