Missing under acceleration

I bought this 2012 Expedition Limited 4x4 last year and I have always had this problem, otherwise it runs great...If I try to accelerate higher than normal like getting on an expressway ramp, the vehicle starts bucking like the engine is shutting down for a second...it is not like a little miss it is quite pronounced. When it would do this I would just back off a little and it would be fine. Yesterday I was on a ramp and had to accelerate harder than normal and it started bucking and popping like a backfire...I let off and it felt like it was down on power then I noticed the check engine light was on. I drove a few more miles on the interstate and the light went off .It seems fine now, but I haven't accelerated hard.
Does anybody have any answers...I am baffled
Thanking you in advance, JOHN

Use a code reader to see what codes it throws.

I am not a mechanic but I had a Navigator with the 5.4 that did what sounds like the same thing and it was the Cat converter. Did a Cat Delete and it purred.

What about the plugs and fuel filter? Also get a little code reader.........cheap

I have a code reader, but I don't know if it will read anything without the check engine light. I'll have to read the owners manual and see if it will work hooked up while driving...Thanks guys I'll let you know

the hogg said:

I have a code reader, but I don't know if it will read anything without the check engine light. I'll have to read the owners manual and see if it will work hooked up while driving...Thanks guys I'll let you know

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Should...........try it

Sounds like a bad coil pack. Mine did the same thing when i bought it. I thought it was everything from transmission going bad to throttle position sensor.

When I would back off the throttle it would run ok. Usually happened on on-ramps.


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Thanks for all of your input...I will check on my code reader tomorrow...
Thanks again, JOHN

COP


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Circumstances have not allowed me to do anything to the Expedition...Had to go out of town and took her Taurus SHO...would rather drive my truck...lol
Should be home soon and start checking out the Expedition...
Thanks Guys,
JOHN

You might get one of the OBD2 interfaces and use Forscan to get a better view of what's going on.... see misfire counts and cyl, read stored codes, etc.

My Gen2 5.4 has a Cyl 4 miss under certain conditions and it's behaved as you describe a few times when in closed loop but before ECT is fully up to running temp. It did seem like much more than a single cylinder misfire. I have not observed the MIL illuminate when my truck had this occur and there was no stored code.

I can most reliably reproduce the misfire in neutral at certain RPM (approx 1900 rpm). If I reproduce the misfire for more than 15-20 sec or so, it will illuminate the MIL, which flashes until the misfire ceases.
Per Ford, under this condition the ECM temporarily shuts off the injector for the misfiring cylinder to protect the cats. I've observed that the misfire becomes more noticeable for that period of time, no doubt because the offending cylinder is a dead hole.
My Gen2 only has 55K miles and the COP/FI connectors appear to be secure so I suspect the COP (or spark plug) but, because Cyl4 COP is such a PITA to work on and the misfire is very intermittent, I haven't yet found the time to repair it.

The $80 I spent for a VCX Nano AMSP239-W (I chose that OBD2 interface for its ISO J2534 capability) saved me more than its cost to program keys and using Forscan is much better than a code scanner as it allowed me to discover which cylinder was misfiring but not throwing any codes.
Any misfires aren't good the the cats so I need to repair mine before it gets worse.