Very Random Stumble/ Stalling

[Willcall]

It's a 2001 5.0 AWD and is Low Emissions Vehicle (California Emissions) equipped. Purchased in November '14 with 104K and now has 130K.

The problem started about 3500 miles ago/ mid June and has happened a total of 5 times. It starts with the car acting as if there is no throttle input (it down shifts fine, as if I were coasting to a stop). When it comes to a stop, it idles fine for a second or two and then begins to miss VERY badly with the RPM dropping very low. After that it (1/5 times) begins running normally again after about a minute or two or (4/5 times) stalls out completely. When this happens, it starts up like normal and then begins stumbling/ stalling almost immediately after. I've noticed that if I turn it off and leave it for 2-3 minutes, it will run normal after that. 3/5 times it happened while idling at a stop, 1/5 coasting from 75 to 55, and 1/5 at full WOT while passing a car. None of these events has triggered the CEL. During the most recent, I was outside of the car couldn't remember hearing the fuel pump whining like I can normally hear it. The fp has whined constantly since I bought the car, but I was assured by a Ford tech that it was probably just an non-factory fp. My fuel economy has stayed the same http://www.fuelly.com/car/ford/explorer/2001/willcall/346830

I hooked it up to my SCT XCAL3, it data logs the fuel pump duty cycle at 1.000 (100% ?) at idle? Also, the fuel trims are between .980 and 1.004 at any given RPM. Is this normal?

I have replaced the TPS sensor (it was bad) and the CPS/Synchronizer (it was squeaking) was replaced in March.

Could this be an intermittent MAF issue? or fuel pump going bad? O2 sensors? Something I'm not seeing?

 

[glentrulove]

Sounds like classic MAF sensor, but could be fuel pump as well, FYI do not buy a Autozone, Oreilly, Advance Auto MAF sensor, spend the money for a napa sensor its well worth your money to not pay for a tow into town.

 

[Willcall]

Still happening

Okay it has happened a couple more times, the car has 137k now. I have now replaced the fuel pump assembly, fuel filter, engine air filter, MAF sensor, and all four O2 sensors.
I finally got it to act up while I was using my XCAL 3, I noticed the short fuel trims dropped from around 1 to .7 and not fluctuate like it normally does, the spark count drops from around 39 to 18. Which explains why it acts as if some cylinders are just turned off. Also, the engine coolant is between 200-208

So failing coils? failing computer? Vapor lock? What could it possibly be?!

 

[pcam13]

Crank position sensor will basically turn the cylinders "off" as will a loose connection on the EDIS blocks. Check your intake air temp sensor and IAC. Either of those fail it will cause issues like that.