What could cause a 2001 Ford Taurus started missing and skipping, and loss of power?

Idles smooth, takes off slow. Sluggish going up hill, but will go faster down hill. Push down on the gas- little change.
Ck engine light is on of course.
Any idea what it could be?

Update: Okay, Shop says bad air flow 'something, and needs tune up. -$530!

Added (1). That did not solve problem-
Codes-
P0102
P0113
P0305

Replaced *** air flow sensor, coil, plugs and wires, catclean… Now $735- problem not solved

Added (2). Shop sent car out to muffler shot to replace catalytic converter. $$?
They are still looking for problem…

Anyone have an idea what could be wrong with this car?

They are not technicians in that shop.
Your dealing with parts replacers who hope they get it right every time you spend money.

Without being there, check these things…

#1
Verify that the Mass Air Flow Sensor wiring is connected properly and that there are NO broken or frayed wires.
Inspect for any air leaks near the MAF sensor.
Make sure there are NO openings in the duct /hose between the MAF & the throttle body

Take a compression test
Check fuel pump pressure.
And While doing that, take a good sample of fuel, let it sit for a few minutes & check for Water in the fuel

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How about any hissing sounds.
Check for broken, split, cracked vacuum hoses.
Especially The PCV valve & its hose
---------------------------------------…
LOOK carefully at plugs within the harness to see if anything is disconnected

With the engine running,
Being VERY careful, wiggle the harness in few spots.
Check the alternator wires.
Does the engine run any different at anytime you touch or move anything?
____________________________________

The EGR & the Idle Air Control Valve
These both deal with vacuum and can cause the vehicle to do what you're saying
If one is stuck in the open position

You mentioned that your car takes off slow. I think that's your problem. Only airplanes and helicopters are supposed to take off.

The wiring harness connector for the MAF and IAT wiring may be loose, damaged or corroded… Have a shop check the wiring harness connections since both MAF and IAT sensors share the same harness connection point. The first two trouble codes relate to issues with the MAF and IAT sensors… P0102 and P0113. If the harness connection issue solves the problem, I'd get my money back from the shop for misdiagnosing the problem and unnecessarily replacing the MAF.although some of the repairs may have been needed… Talk to the shop owner to credit at least the labor part.

http://www.taurusclub.com/forum/82-maintenance-repair/161060-simutaneous-code-p0113-p0102.html

The third code P0305 relates to a misfire in cylinder #5 which could be caused by a number of issues… Bad spark plug, plug wire, bad injector, low compression, etc. A shop would have to further diagnose issues with the # 5 cylinder… Swapping the spark plug or injector with another cylinder can show if the problem follows the plug or injector and sets a trouble code for the other cylinder or not which may indicate a bad plug or injector. Given the age of the car, it would be a good idea to run some Seafoam or Techron in the fuel tank per label directions to clean the fuel system and injectors.

They can also do a compression test to see if that cylinder is low on compression compared to other cylinders which might indicate a bad valve, etc. Compression values should not be more than 15% below the highest reading on any cylinder… I.e. If the highest reading of any cylinder is 200 psi, the lowest reading for any others can't be below 170 psi.

"Causes
A code P0305 may mean that one or more of the following has happened:

Faulty spark plug or wire
Faulty coil (pack)
Faulty oxygen sensor(s)
Faulty fuel injector
Burned exhaust valve
Faulty catalytic converter(s)
Running out of fuel
Poor compression
Defective computer

http://www.obd-codes.com/p0305