hesitation on acceleration

[and0r]

LOL

 

[Joemz9]

Have your cats checked same symptoms i had on a Contour.

 

[GAINMOB]

Check ur voltage as well... surprisingly it is a symptom I've experienced twice when my alt was dying

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[poorboy1964]

Howdy all,
1998 5.4 Eddie Bauer, 225k
Lately been suffering some rather severe hesitation/sluggishness on acceleration (bottom of the power band), then smooths out. Happens on acceleration from standing start, from acceleration at road speed, as well as at highway speed.
This only happens upon restart after truck has been sitting for an hour or less. Runs perfectly on initial start/drive or after it's been sitting for a few hours.
Truck never stalls out, but acceleration is quite challenged.
It was suggested that perhaps "bad gas" but several tank fills and bottles of conditioner and gas line anti freeze has not resolved.
Fuel filter was changed 7 months ago. Plugs and COPs are a year old.
No idiot lights on dash.
Any suggestions are greatly appreciated.

Question do you notice this happen when engine is warmed up?
I'm asking because I have had this problem for a long time now and have tried all of the things listed above when engine is cold it runs great. There is a Ford TSB out that talks about it but it requires a re flash from ford

 

[1955moose]

My guess is a failing fuel pump. Do a fuel pressure test. When these pumps age, they don't always go out all at once, some do. What happens to some is they do exactly what your describing. Kinda like a human that has a failing or clogged heart. We keep on going but labor to do so, especially when our bodies get loaded, like walking uphill, or trying to lift something. If your pumps failing, instead of pumping the necessary 35-55 psi, it drops down to 10-25 psi. Enough to fire and run, but labors under load. Check pressure and report your findings.

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[rjdelp7]

My guess is a failing fuel pump. Do a fuel pressure test. When these pumps age, they don't always go out all at once, some do. What happens to some is they do exactly what your describing. Kinda like a human that has a failing or clogged heart. We keep on going but labor to do so, especially when our bodies get loaded, like walking uphill, or trying to lift something. If your pumps failing, instead of pumping the necessary 35-55 psi, it drops down to 10-25 psi. Enough to fire and run, but labors under load. Check pressure and report your findings.

Sent from my N9131 using Tapatalk

Ford fuel injectors, need at least 45lbs of fuel pressure. I have been told 40lbs or below will affect how it runs.

 

[1955moose]

I'm guessing he's probably way below 30, we'll see!

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[Flamesfan]

Question do you notice this happen when engine is warmed up?
I'm asking because I have had this problem for a long time now and have tried all of the things listed above when engine is cold it runs great. There is a Ford TSB out that talks about it but it requires a re flash from ford

This lurching/sluggish acceleration never happens when the truck is cold, after being parked overnight or for a few hours.
An hour or less, and the lurching/hesitation occurs.
If I continue driving, it will (eventually) smooth out and not happen again during the current trip.
Normal acceleration restored.
It is never hard to start, warm or cold, it has never stalled, and the curb idle when it is being sluggish is normal, or is near enough that I dont feel the difference.

Today was the worst of it, came home for lunch during my workday, truck was off aprox 30 mins, and driving back would barely climb the speedometer. Though it eventually would, it fought hard.
Today also marked the first time the check engine light showed itself...flashed steady for about 5 mins (or less), then didnt come back on.
Engine smoothed out, and acceleration was normal the remainder of the drive.

I dont have a code reader so heading to my nearest NAPA in the morning.

 

[Flamesfan]

Turns out the only code that came up was a #4 misfire.
So, I guess it could've been worse...could've been a #8

Thank you all for the suggestions and ideas. Very much appreciated.

 

[Starkman]

Did this condition ever get fixed? Mine started doing this today. It is mid 90s today and read one solution is the MAP sensor.