90' XLT w/ 5.0 fuel issues

[ablediver]

I'm having a problem with acceleration in my 90' Bronco FS XLT with a 5.0. The vehicle has been stored periods up to 4-5 months (absent due to work) at a time. The tank has been filled and treated with red STABIL every time after use. The fuel tank was dealer replaced in 1999. The tank gauge sending unit was dealer replaced in 2015. New plugs and rotor in 2018 ( 2k miles since). The fuel filter was dealer replaced in December 2021. I use regular (87 oct) gas in it with no detonation.
OK, that's the history, now here's the story: When it's been sitting, the first several miles have some hesitation, but fairly good acceleration, but afterwards, it "stumbles" or " bucks" from standing start unless you plant the pedal down about a third of the way and then it goes back to a noticeable 80% power feeling. This begins all over when you come to a stop. I figured with a fresh tank of gas and a new fuel filter, it would fix this issue. That didn't change anything. I'm back to square one. Anyone have a similar experience with a successful remedy? Appreciate the reply.

Ablediver

 

[Skitter302]

Check for KOEO and KOER codes to start with but it sounds like a vacuum timing issue.

 

[ablediver]

Check for KOEO and KOER codes to start with but it sounds like a vacuum timing issue.

So, like I'm the dumbest guy in the room here >>>> Are you saying I get a code reader and look for KOEO (KEY ON / ENGINE OFF and KEY ON / ENGINE RUNNING (?) Codes ?

 

[ablediver]

Or, should I complete an HHS-1157, and a FOH-52 and combine that with a CDC-17 ?

 

[miesk5]

So, like I'm the dumbest guy in the room here >>>> Are you saying I get a code reader and look for KOEO (KEY ON / ENGINE OFF and KEY ON / ENGINE RUNNING (?) Codes ?

Yo ABLE,
Instead of buying a code reader, try a Self Test for Diagnostic Trouble Codes (DTC)s by my pal here, BroncoJoe19 @ Code Reader
EEC AKA PCM, computer stores the Self-Test program in permanent memory. When activated, Self-Test checks the EEC system by testing memory integrity and processing capability, and verifies that various sensors and actuators are connected and operating properly.
The EEC will tell you what it found out by testing your sensors, and also any stored information it saved from anything that went wrong during the last 40 trips.
●The engine temperature must be greater than 50° F for the Key On Engine Off (KOEO) Self-Test and greater than 180° F for the Key On Engine Running (KOER) Self-Test. Run it around to heat the engine up and shift thru all gears including Reverse. Make sure A/C is off and transmission is in Park (automatic); or in Neutral for a Manual release clutch. Then turn off engine, all accessories/lights (close driver's door) , etc.
Do KOEO test First. Post Code(s) here according to KOEO & KOER.
A helper can assist you by counting the codes. Some use their smart phones to record them.
BEWARE OF FAN, BELTS, PULLEYS, HOT HOSES, IGNITION HIGH TENSION WIRES, AND ENGINE COMPONENTS
Or ask local mom and dad parts stores if they will test it for you.
Al

 

[5 Star Garage]

I'm having a problem with acceleration in my 90' Bronco FS XLT with a 5.0. The vehicle has been stored periods up to 4-5 months (absent due to work) at a time. The tank has been filled and treated with red STABIL every time after use. The fuel tank was dealer replaced in 1999. The tank gauge sending unit was dealer replaced in 2015. New plugs and rotor in 2018 ( 2k miles since). The fuel filter was dealer replaced in December 2021. I use regular (87 oct) gas in it with no detonation.
OK, that's the history, now here's the story: When it's been sitting, the first several miles have some hesitation, but fairly good acceleration, but afterwards, it "stumbles" or " bucks" from standing start unless you plant the pedal down about a third of the way and then it goes back to a noticeable 80% power feeling. This begins all over when you come to a stop. I figured with a fresh tank of gas and a new fuel filter, it would fix this issue. That didn't change anything. I'm back to square one. Anyone have a similar experience with a successful remedy? Appreciate the reply.

Ablediver

Take a look at your accelerator pump.

• Another symptom of a faulty accelerator pump is engine sputtering or stalling. The sputtering is caused by the lack of fuel that is supposed to be provided by the accelerator pump when throttle is rapidly pressed.

 

[ablediver]

Thanks . Will do

 

[miesk5]

Yo Ablediver,
Is your 90 carbureted?
If stock and not carbed, you won't havevan accelerator pump.

 

[ablediver]

Original EFI. Stock. Thanks for the follow / up

 

[5 Star Garage]

Yo Ablediver,
Is your 90 carbureted?
If stock and not carbed, you won't havevan accelerator pump.

My bad, don't know what I was thinking. Thanks

 

[miesk5]

My bad, don't know what I was thinking. Thanks

Yo 5,
I've had too many days like that!
Suggest you introduce yourself and your Ford(s) in Introductions section soon.
Be well!
Al