If you get a P0401 code take off the throttle body at the intake manifold and clean out the passages there from the EGR valve before looking anywhere else. A lot of folks here seem to have replaced a lot of parts before discovering this. Apparently these cars are prone to these passages gunking up that can completely block the EGR flow. While this may sound good it is not as the PCM is tuned to work with EGR. You need a 1/4" drive and a couple of sockets to take off the intake hose, air cleaner housing and the throttle body along with a few electrical connectors and hoses but the job is not hard.
Use a small pick and hook set or a stiff wire to scrape out the passages along with some carb cleaner, (make sure it is O2 sensor safe). Stuff some tissue paper in the manifold to keep the gunk out of there. I used a small plastic philly cheese container from below to catch the gunk from falling all over the engine.
A word of note, the caution label on the throttle body and in the FORD service manual on not cleaning the throttle body or plate because of a special coating is likely to keep someone from physically scraping the alloy body and throttle plate. My throttle plate was just as gunked up on the manifold side as the intake manifold passages and needed a good cleaning.
Just use a normal solvent and a brush to clean up the gunk. I beleive the "coating" is just teflon which is not attacked by normal solvents. Just do not scrape the coating or the alloy housing. I also took off the throttle position sensor from the throttle body before the cleaning to keep the solvent out of it.
Also use a new throttle body gasket - Ford part number F5RZ-9E936-A, (about $6.00 CDN). Do not even think about using the old gasket as it is a false economy and could result in intake air leaks.
Code P0401 now gone. Engine seems to run better as well.
Cheers.
