These could be related or not... it's hard to tell at this point. The P0405 is usually a defective DPFE sensor, but normally that would not cause all these other issues. I once had a defective brake booster which caused a vacuum leak with hard brakes and a rough idle. You can test this by removing the vacuum hose from the booster and plugging it off to see if the idle corrects. An area common for leaks is the intake gaskets. The easiest way to test this is with some carb cleaner spray. Spray it all around the intake area and listen for a change in idle indicating it is sucking the spray up through the leaky gaskets. Another area to check is the PCV hose elbow coming from the intake. These have a tendency to get soft and suck closed or split open.
Ok, the flashing light is telling you there is a serious misfire and to not drive the vehicle. Since you continued to drive with the serious misfire it could have damaged the catalytic convertor. The raw fuel will cause the convertor insides to melt. This will cause the convertor to plug up and restrict the exaust. In turn this high exhaust backpressure will cause a serious lack of power and lower engine vacuum since the air has no where to exit. This could have been a problem that started out as a simple bad coil pack (they fail all the time and are most noticeable in wet weather) and progressed into a more costly issue. There is a good chance that the EGR code is setting due to the high back pressure in the exhaust. The best way to check is to remove an oxygen sensor and use a back pressure gauge. I figure you don't have this tool, so you can try loosening the exhaust at the convertors and see if that restores engine power.
Great advice, I took it apart and the front (light off) converter was plugged. I think the rear converter (not the light off) on the exhasut pipe has a partial restriction too. The engine seems to be more sluggish with that part of the exhaust hooked up. One thing that I noticed is that when the vehicle is in park, you can't rev the engine passed 4000 rpm. Is that a rev limiter or is their a possible fuel delivery problem? The engine seems to pull strong to 6000 when driving it down the road. Thanks so much for your help!! I will accept your answer as soon as I hit the reply button.
There is a park/neutral rev limiter but I don't know what the actual number is.... You may want to contact Ford about a convertor warranty, they should be 8 year 80000 miles.
I would say the misfire caused this problem and 99% of the time a bad coil is what causes the misfire! I see them go bad all the time.
It has been a few weeks and the car is giving me trouble again. The exhaust was fixed, all plugs were replaced, along with the fuel filter, air filter and intake gaskets. I am now getting the following codes P0300, P0304, P0305 and P0316. Any ideas? I have not replaced any coils yet. The problem arose after the vehicle sat over a cold and very rainy weekend. I realize this is a new question but I wanted you to see the history from the older posts. I will gladly pay you for help with this question.
What was fixed on the exhaust?
Typically if the misfire starts during or right after raining you have a problem with the coil. You can remove the coils and look right where the electrical connection is. You will probably notice a small crack from the plug area heading to the center of the coil. I believe this is where the water enters. With the coil removed, remove the rubber boot and twist off the spring. You will likely see a small amount of corrosion on the end of the spring and also on the tab sticking out of the bottom of the coil. This is a sure sign that moisture was in there. Since the coil is an electronic device.... water is a big no-no. If you see any of these signs then replace those coils. If everything looks clean and shiny then swap the #3 and #5 coil and see if the misfire change to cylinder 3. If it does then you know you have a bad coil.