Purchased a used 2006 Taurus; was idling rough. Changed fuel filter, a mass air sensor, and a idle control sensor, still idles rough and now displays check engine...what on earth could be the cause

Hi, is your air filter clean,any trouble codes,throttle body clean,idle air control passage clear,idle air control module.

MAF (mass air flow)sensor or o2 sensor and exhaust MAF can be cleaned many sites tell you how too

CLogged fuel filter, weak or faulty pump, clogged air filter etc. Chech all filters and vaccum hoses for leaks.

Get a full tune up, how is your gas millage? if your gas millage is bad then you should suggest changing your o2 sensors.

Well since you changed all of those things there are still come other culprits that can cause rough idling. Another cause of a misfire or rough idling may be a coil that is not functioning properly. Also Sensors that are not reading correclty. The most possilble sensors would be the mass air flow sensor, idler air control, or o2 sensor. They all have control in telling your control module how much air is entering in the engine so that it can determine the appropriate amount of fuel that needs to be used with that air for combustion. If its burning a great amount of fuel then the system is running rich. Have your local parts store check to see if you have a codes.

Hope This Helps!

Idle Air Control Motor That Is Dirty, Or Faulty. Good Luck

spark plugs changed too? next guess is MAF (mass air flow sensor.

I had to replace the mass air flow sensor. $ 150. the engine would shut off when driving too.changed fuel filter only worked for a day. The sensor is just after air filter.

A code P0174 may mean that one or more of the following has happened:

• The MAF (Mass Air Flow) Sensor is dirty or faulty. Note: The use of "oiled" air filters can cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry.
• There could be a vacuum leak downstream of the MAF sensor. and your solutions are.
  • In the vast majority of cases, simply cleaning the MAF sensor does the trick. Consult your service manual for it's location if you need help. I find it's best to take it off and spray it with electronics cleaner or brake cleaner . Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstalling
  • Inspect all vacuum and PCV hoses, replace if necessary
  • Check for a dirty fuel filter and proper fuel pressure

Check your idle air valve, maybe your air filter needs to be changed. EGR valve may need to be checked at as well.