Here is a list of basic checks to perform:
1. Make sure the oil dipstick is secure in the dipstick tube. Check the engine oil level to make sure it is not overfilled.
2. Visually inspect the air intake tube for leaks. You can spray some carb cleaner around the tube and see if the engine idle increases.
3. Perform the same check around the intake manifold to test for leaks.
This is where the tests get more complicated:
4. Check the fuel pressure. The fuel pressure should be between 55-65 psi with the key on and the engine off. Use the test port on the fuel rail (as shown below) and a fuel pressure gauge (as shown below).
To perform the next tests, you will need a Ford Scantool that can perform the necessary
circuit tests. Here are the next items that should be tested using pinpoint test procedures.
5. Mass Air Flow Meter
6. EGR valve, DPFE sensor, and EGR backpressure transducer
7. Wiring failure in the Oxygen sensor circuit. You must check sensor output signal to the PCM to make sure there is not a wiring issue between the O2 sensor and the PCM.
The most common issue is the Mass Air Flow Meter but you should go through the diagnostic process to make sure before guessing.