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What size engine do you have?
What is the 8th digit of your VIN #?
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.
First spray around the intake manifold with carb cleaner to check for intake leaks. Leaks in the air induction after the Mass Air Flow sensor will cause the engine to register both of these codes.
You will need a scantool to check the flowrate on the fuel injectors however. A leak in the fuel system can cause these codes as well. Check the fuel pressure to make sure you don't have a leak at the regulator or from an injector.
The trick is that you're dealing with a failure that throws a system too lean code but no other failure code.
Things like a fuel pressure leak, sticking EGR valve, intake manifold leak, intake air tube leak, ect. will cause these codes to come on but not trigger other failure codes.
I have seen this issue quite a bit, but the mass air flow sensor usually solves the issue.
I have found a Technical Service Bulletin for checking for leaks in the intake manifold with a smoke detector machine. Unfortunately this is probably something you will have to take to the dealership to have tested because the test machines are expensive. If you have it tested and need to replace the intake manifold/gaskets I can give you the procedure so you can do it yourself and save some money.
Here is the Technical Service Bulletin:
DIAGNOSTIC PROCEDURE FOR LOCATING LEAKS WITH THE ROTUNDA'S VACUTEC - 522 SMOKE LEAK DETECTOR MACHINE
Thank you fro helping me with my explorer it did end up being upper and lower intake gaskets and a valve cover gasket.. you said you could give me the procedure to do this i would appreciate it if you could thank you so much