Rough Idle

Go to this link: https://www.2carpros.com/articles/engine-misfires-or-runs-rough

My Ford Taurus is running a little rough. I have had the car checked for vac leaks with a smoke mach and given it several gas treatments. Replaced plugs 6 months ago, all gapped properly. The computer is showing 29.6 mpg (I take some long hiway trips). Also, why does the AC compressor cycle on every 14 sec or so even if I am using the heater? I can feel the car surge and the RPMs jump when this happens and it is driving me crazy. On vent setting (11 o'clock position on air select dial) this does not happen, on all other settings it does. Car has 123K on it. Thanks.
Topcat1961

Check A/c system as its sounds as low on refrigerant

The air inlet door vacuum control motor is at no vacuum, admitting only outside air into the passenger compartment.
The panel/floor door, defrost door vacuum control motors are at no vacuum, directing airflow to the defroster duct and the side window demisters.
The temperature can be adjusted to heat or cool the air below the outside temperature.
The A/C compressor will operate if the outside temperature is above approximately 6°C (43°F).
The blower motor is on.

Ok, BMRFIXIT, this is all very intresting but, if I am understaning your reply properly, the answer is : Yes, the AC compressor will cycle on and off in every setting on the dial except the air inlet setting which is located at the 11 o'clock position on the dial.
Is this correct or not? Also, I would like to know someones thoughts on the rough idle part of the question as well.
Topcat1961

My understanding its happening only when AC compressor on

and if so 1st should have the AC charged and Check for leaks

My car idles rough mostly when cold. Also when braking and coming to a stop, car will hesitate and feel like it is going to stall. This will continue when stopped and as I am accelerating from stop. When on the highway, it seems to run fine. I have replaced the mas airflow sensor. When checking codes I get P0174 and P0171. I understand these codes to indicate a number of different things, like vacuum or oxygen sensors. But these codes indicate oxygen sensors on different banks. I'm not finding any obvious vacuum leaks. I also change the fuel filter. Please help, I'm going around in circles.

Its an indication of a vacuum leak
best to have it smoke tested
if can not find the leak visually
most common to find intake manifold and gasket
check PCV valve hose too

Had transmission rebuilt less than 2 months ago. Now I have been having periods of intermittent rough idling and hesitation when pressing gas pedal either from a start or when getting on the freeway. I have changed the spark plugs, wires and fuel filter.
Code that comes up when checked is P0353 Ignition Coil C Primary/Secondary circuit malfunction.

Have you checked wiring to the coil to make sure everything is tight, clean and undamaged?

All wiring to the coil looks to be in good shape and tight at connections.

If that is all good, I would think the coil is bad. You may want to remove it and have it checked.

primary and secondary coil ohn test showed the coil to be good.

There must be a wiring issue. Check to make sure wires are not damaged.

after checking all the wiring and connectors for anything that looked like it could be bad I decided to change the ignition coil and have not had any problems since changing it four days ago.
Thanks for the great advice.

Great! Let me know if you have questions in the future.

Joe