Truck: 1998 Expedition 5.4L XLT 4x4
Miles: 345,000 (#1=166k, #2=179k)
Bolt on: HiFlow Cats, Magnaflow Cat back, BBK Cold Air Intake, Accel COPS, matched injectors, Edge programmer.

No funny spots on parking spot, Oil is fine, coolant is fine, Trans oil a bit high.

For the past month my Expy has had increasing instance of low speed stumbling , and now recently stalling and dying during takeoff and in parking lots. Usually after sitting for a few minutes, it will run normally and I can continue. It was occurring every other time I drive the truck. I was able to complete a day trip of 600 miles without a hitch, and today it will not start.

When the stumbling starts, pressing on the gas causes the truck to slow down, and tapping the gas pedal has no positive effect. I can smell gas in the exhaust after it dies.

There are no codes

What I have tried in order:
1) Cleaned filter and MAS, checked for vacuum leaks, checked for grounding positive wire,
2) Replaced IAC - no change.
3) Replaced TPS - better shifting but issues are still getting worse.
4) Removed Edge programming to stock, removed battery to reset PCM - Will not start now.

I have reviewed 20+ "Stalling / Stumbling / Rough Idle" posts here and there. It does seem there is a lot of meaningful advice, but never a resolution from the OP.

Payday is Wed.. so I was thinking of calling in sick and:
1) Remove TB and down tube for scrub
2) New plugs
3) New Fuel filter
4) Lit match in the tank..

What say the unwashed masses?

My Chevy/Jeep bros say it is the name plate..

 

Check the injectors for a leak. How many miles on the plugs?

 

wow... grrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr

Busted in on my neighbor with the fancy code reader and went for what I thought would be a short drive.. like the end of my driveway, and readied the kids to help push me out of the street.

... and off we go, 100 yards, a mile, freeway, another 5 miles, found a dirt lot and did some 4x4 doughnut's, 2 miles though a neighborhood at 20 mph, over speed humps, stops, goes, around the airport, and back home.. not one code, not one misfire, nothing....

grrrrrrrrrrrrr.....

 

Thanks Blue.. I think there are 60k on the plugs. No leaks at the fuel rail. She ran strong and happy for 30 min tonight.. I just happen to mention I was looking at a used Grand Cherokee in front of her..

I think I know why they are "she" now...

 

Piled on another 10 miles of happy driving in 110 degree heat with freeway and street mix, with a stop for gas and icee in there.

Perhaps it was the TPS after all. That, the Edge removal, and the computer reset were the last things I did. No stumble since.

 

Update..

Three days without a hitch when it happened. She made it just far enough away that in 110 it was not fun to walk, so I rang the spouse.. just call it ground work for a new truck.. P-). This was with the "cleaned" IAC vs the new one and battery disconnected for 2 hours.

I then put the new IAC back in and I left the battery disconnected overnight.

Before church in the morning, I buzzed by to check on her, and she fired right up. I drove her home and she sat for a day.

 

update...

This afternoon she started, ran the truck all over the neighborhood about 8 miles of rabbit starts (I know... hehehe...) bumps, twists, 105 degrees outside, A/C cranking out cold. Not a hitch.. until....

Rolling into the driveway - she bucked and stumbled. now will not start.

Pulled the battery cable and waited 30 min.. BOOM, starts right up.

What other sensors can there be that cause her to stumble and die.

 

Note to self - Other stuff to try...

EGR valve, EGR vacuum solenoid, spark plugs, wires, coil packs, battery, fuel filter, DPFE sensor, PCV valve. I have cleaned the following components/systems with sea foam or respective cleaners: throttle body intake, exhaust, fuel, oil, and MAF sensor.

 

Last night I:

1) Removed throttle body and throat, soaked in Seafoam and scrubbed with a toothbrush.

2) Installed new plugs and checked the fuel injector caps and cops.

3) Disconnected the battery

4) Tried to change the fuel filter - but that crazy "quik release" tool did neither.

Ran it 20 miles up and down the freeway in 110 degrees with A/C running today, ran like normal - smooth, easy, noisy (it was 800 watts of Van Halen).
Tried it again just two hours later, at 90 degrees. Got 100 feet - pushed it home... same symptoms.

 

Today after overnight with the battery disconnected. Start, drove 20 miles, stutter and die, this time leaving me 3 miles to walk in the 105 degree afternoon.

Installed new EGR Vacuum Solenoid, EGR Valve Pressure Sensor (DPFE), shot some TB cleaner down the two hoses.

Reattached battery, started up, ran for a min, sputter, and die.

Still no codes, but I keep having to clear the PCM to start it.

wits end.. I am at...

 

last thing I could possibly install.. the EGR its own bad self.
Put it on, started up, drove home.

and lots of very specific prayer..

Could this be it? Tune in tomorrow..

 

Have you checked the fuel pressure? Probably not it.

An intermittent problem like that indicates it might be electronic, in the ignition or computer.

 

Started up this afternoon, drove 12 miles with A/C blowing in stop and go traffic, go to my destination.
Loaded the truck up with sailing essentials.
Started up, drove 12 feet - right to the edge of a busy 8 lane city street with rush hour traffic buzzing all over it.
Waiting for an opening.. one stumble and DEAD.

No codes.
No warnings now
- just death.

whew, but, poooo.

So - new theory.

The truck hits normal operating temperature and drives fine until I have to stop. Then will not start. What changes when it hits that magical point?

Fuel Pump?

 

Maybe crankshaft position sensor?

 

Tried another "fix" for the stall after reaching operating temperature. Pulled the O2 upstream connectors. Some said it would just run lean, but now it will not start at all after getting me 100 feet. Reconnected and now waiting for the PCM to reset....