Shaking and Check Engine Light Blinking

The P0171 is a lean code that could be caused by a vacuum leak, but that would not cause it to shake and the engine light to blink. The the shake and blink are mostly likely caused by the P0316 and P0302, which is a cylinder 2 misfire. A simple tune up could fix that, it could have a bad coil, or a more serious issue like low compression. I can't I would take it in to have it looked at asap. It is not good to drive it like that. The engine light flashing is a sign that it needs to be serviced immediately.

Sounds like you have a clogged muffler or catalytic converter.

Is it weird that my friend unplugged the battery for a while (to reset it - something he read online), and it's running a lot better now? The check engine light is now off and it's not shaking as badly (just a minor tremor is still present when in drive and shaking when applying brakes). The shop isn't ready for it for a couple days, and I'm wondering if I can/should be driving it. Hate for something more major to be going wrong.

Did you find out what was going on? The same thing is happening to mine!

I own a 2005 Ford Freestar, and also feel the uncertainty of driving this minivan. Recently I have noticed that my minivan started acting up after a few days of heavy rain. Ford is aware of this issue, and for this reason they issued a Technical Service Bulletin (TSB 06-14-10.) Seems to be that a lot of the issues with this vehicle are related to this problem, water in the ECM. Once the ECM is waterproofed, then you can consider other minor problems like a bad sensor.

I own a 2005 Ford Freestar as well and it does the same thing after Rain or water splashes up on the under carriage. One of our techs, not a ford mechanic, is suggesting its something electrical getting wet and causing a short? It started happening after i was forced through a rather large puddle, but now it only takes a small amount of water for it to start acting up....any suggestions?