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Discussion Starter #1 (Edited)
The Car:
2011 Fiesta 5MT 149,000mi

The Problem:
When driving or idling the engine will turn itself off. No check engine light or trouble codes. When it shuts down the Power Steering Malfunction warning shows on the radio display but I think this is secondary to stalling. While it runs the idle is smooth and throttle response is quick and linear. When it stops its just like turning they key off, not stuttering or pulsing just straight off. The only warning light displayed is for tire pressure (despite tires being full) but this has been a problem for the last year.

What I've done so far:

I first checked the battery voltage while sitting (12.6v) and running (14.2v). My suspicion was a ground problem so I ground and greased the grounds as recommended in the "
Diy:tsb 10-19-6" thread. I checked the fuse box which was very dirty but none of the fuses or relays had visible corrosion on the leads. I did brush any fuses and relays that would affect ignition, PCM, or fuel pump, to no avail. The car has not had the battery junction box service which is now expired bit I'm going to try for a good will repair. The car has been under my care for nearly 2 years and 50,000 miles and has been perfectly reliable, this is the first sign of an electrical issue.

Edit:
Here's my current plan. I'm going to clean the throttle body and MAF just to rule out those (although if they were bad I would expect to get a code and have rough idle). My vin does not fall under the battery junction recall but Ford said they might be able to do something if I have a positive diagnosis and labor quote from a dealer. If cleaning out the intake doesn't do the trick, I'll get it in for diagnosis at the dealer then see if Ford can help me out. Anything else I should do before then?
 

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Edit delete. I see where you have inspected the power distribution box. Be sure there are absolutely no signs of corrosion.
 

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Discussion Starter #3
I went through the fuse box and sprayed all the contacts with Deoxyit d5 let it sit for a few minutes and then repeated again. I did this for every fuse and relay under the hood as well as the PCM to harness connectors. I also replaced any fuses with visible corrosion on the prongs. The car still has the same problem. It starts fine and runs well for 5 to 10 minutes then just shuts off. Ford said my Vin was not covered by the (now expired) customer satisfaction battery junction cleaning so I guess I'm out of luck.
 

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Discussion Starter #4
Update: The plot thickens...

I decided to clean the MAF and TB this evening, fully expecting nothing to change. Surprisingly it seems the problem has lessened. The car still stumbles every 5 to 10 minutes but it catches itself and returns to idle. I'm debating between where the Deoxyit needed time to work and break the corrosion in the box or the intake cleaning actually worked. What do you think? How should I proceed in trying to get it to completely stop stumbling?
 

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Discussion Starter #5
Update: solution

I just wanted to post the solution in case any body runs into this thread in the future. We took it to the dealer for diagnosis and they said it needed a new engine wiring harness (due to corrosion) and possibly a new PCM. I went through and inspected and cleaned all the connections and found no sign of corrosion so off to a new dealer it went for a new PCM and now it runs great. It's weird that it just crapped out after 150,000 miles of service but I guess life is strange sometimes. I hope this helps someone in the future. Cheers!
 
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