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Discussion Starter · #1 ·
Good afternoon. My daughter has a 2012 Fusion with the 3.0L. Starting two months ago, the engine will randomly shut off when coming to a stop. Put it in park, crank it up and it goes like nothing happened. No warning, no lights, no shuddering, no codes. It might do it a couple times a week and then nothing the next week. Our mechanic and the local dealership can find nothing wrong with it and can't reproduce the issue. Is anyone familiar with this?
 

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Did you happen to get the report from their scan of the codes? (Any pending codes?)

I’ll assume a code reader was used that reads all the Ford specific codes, not just the basic emissions codes as required by the EPA.

No codes stored or pending is a lot of information all by itself. It means that none of the sensors, solenoids, etc. are the problem. The problem is outside of the OBD-2 control system.

If cleaning the MAF doesn’t solve it, the next two things I’d begin taking a real hard look at are the fuel injection system and loose/bad electrical connections in the wiring harness related to the fuel injection. Including the grounds!

Electrical problems with the ignition system are a possibility, but I’d expect something going sideways in the ignition might bring up a code.

Let us know what you find.
 

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Discussion Starter · #5 ·
Okay, so there were no codes when it came back from the dealer. Last night I was finally able to change and clean the MAF sensor. Both were spotless before I started but I did it anyway. Nothing seemed loose at the time but I didn't get much of a chance to check because it started raining.
 

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If you get to the point that you need to see what’s happening with the car while it’s being driven, here’s what I use when I need to look at the data the computer sees and what it’s doing about it. The Short Term and Long Term Fuel Trims helped me quite a bit.
Rectangle Font Material property Electric blue Gadget



You can watch the Fuel Trims (high trims could be a vacuum leak) and see things like the O2 sensors switching on and off.

It isn’t quite as complicated as it looks, and is fun to tinker with on a Saturday in my opinion. I used it to track down some problems on my son-in-law’s GTP. He drove, I watched what the car was doing on my iPhone.

There are other scanners and software that will do more but this one I thought was fairly intuitive.

Sure beats paying a shop to not fix it!
 

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Hi, my sister had a 2011 Fusion with the 3.0L, with a similar problem. It turned out that mice were chewing on the wires, because Ford is using a plant-based plastic to sheath the wires. Check for mice droppings around the top of the engine which will tell you if you have that problem.
 

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Discussion Starter · #8 · (Edited)
The wires look clean. Down in Florida we don't have much of a problem with wires getting chewed. I ended up replacing the MAF sensor and it ran fine for a week. Now she just called me and it stalled at a gas station and she had to limp it home. She says it's running rough if at all and the wrench light came on. I'm starting to think throttle body. Is throttle body cleaner legitimate or is it like the blinker fluid joke?
 

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Discussion Starter · #15 ·
I replaced the throttle body and gasket over the weekend. Cleared the code and drove it a couple times for two or three miles each and it's running fine. We'll just keep an eye on it for the week and hopefully that's it. Thanks ya'll.
 
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