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'96 Bronco 5.8L. 2.5" Tuff Country lift w/ extended radius arms, 33" Duratracs. Saginaw swap.
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33 Posts
Discussion Starter · #1 · (Edited)
Here is an example of what I mean by "fluctuations": my video

PROBLEMS: Constant engine fluctuations during all types of driving/idling. Random engine surges (ie: turn on truck and rpms jump to 2500 or while cruising, rpms will randomly jump wayyy up there momentarily). Stumbles, definitely lacking power on acceleration from a stopped position.

BIGGEST PROBLEM: On a very hot day doing a long drive through the North Cascades, my truck stalled while cruising down a hill. Just died immediately. Would not start for 45 minutes. When I tried to start it within the 45 minute time period, it would stutter at a very low idle and I couldn't give it enough gas to keep going, it just died. For some reason, after letting it cool down- it started again. However, on my next downhill I decided to switch into neutral (automatic trans), and the second I shifted in, the truck died just like before. Only took 20 minutes of cool down that time to get it restarted.

RANDOM OBSERVATIONS: Ever since I replaced my fuel tank and refused to replace the pump (years ago), the pump has whined super loud. I noticed today that when I'm sitting in my truck in park, while its running, if I apply the brake pedal, the pump whine gets quieter. Like its not working as hard? Or maybe receiving less power? Does this have anything to do with anything??

After looking at a few different forums I tried unplugging the SPOUT (spark output) connector to see if that made a difference while the truck was running. Did not make any change.

OBD1 CODES PULLED: 111 "everything is okay" that is helpful.

ALREADY REPLACED:
-Distributor cap, rotor, spark plugs and wires
-Idle Air Control Valve
-MAP Sensor
-Throttle Position Sensor
-Fuel Pressure Regulator (replaced this during a time where I had constant HUGE engine surges, checked the vac hose and it was wet with fuel, changed the part and surges went away- no change though in small fluctuations)
-PCV Valve Grommet (cleaned PCV)
-ICM
-Fuel Filter

No apparent vacuum leaks.

Just advanced the timing 3 degrees so it could be at 10 BTDC.

Appreciate everyone's advice! Please and thank you!

1994 5.8L 351W E4OD Trans 175k miles
 

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Charlie don't surf..
'92 Ford Bronco XLT
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16,089 Posts
@truester.rooster add your Bronco details to your profile, that way we know exactly what we're dealing with..Year, engine/tranny combo and so forth.

Since you're getting a passing code 111, you might be staring at your answer here..

RANDOM OBSERVATIONS: Ever since I replaced my fuel tank and refused to replace the pump (years ago), the pump has whined super loud. I noticed today that when I'm sitting in my truck in park, while its running, if I apply the brake pedal, the pump whine gets quieter. Like its not working as hard? Or maybe receiving less power? Does this have anything to do with anything??

These pumps all whine to a certain extent but they will start to whine louder when they're on their way out..I'd start by checking your fuel pressure and then we can go from there. Don't throw any more parts at it until you do that.

For reference, engine running you should see 30 to 45 PSI, key on engine off 35 to 45.

Check out this link: Part 2 -How to Test the Fuel Pump (Ford 4.9L, 5.0L, 5.8L)
 

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Registered
'96 Bronco 5.8L. 2.5" Tuff Country lift w/ extended radius arms, 33" Duratracs. Saginaw swap.
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33 Posts
Discussion Starter · #4 ·
Thank you!
 

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'96 Bronco 5.8L. 2.5" Tuff Country lift w/ extended radius arms, 33" Duratracs. Saginaw swap.
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33 Posts
Discussion Starter · #5 ·
UPDATE: Timing was retarded by 3 degrees, timing adjusted and now although the truck is running better overall- root issues still exist.
 

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Yo truester.rooster,
I missed this thread!
yo J,
This is from 94 PCED (PARTIAL)
This 1994 Service Manual provides information covering Emissions for all 1994 Ford Motor Company Passenger Cars and Trucks except the 3.8L Mustang and 4.6L Thunderbird/Cougar vehicles which are covered in the Powertrain Control/Emissions Diagnosis OBD II manual. Complete emissions related diagnostic procedures for all affected systems or components are covered in this manual.
Diagnostic Routines Symptom Flow Charts — Chart 11 -
94 Surge Accel and Cruise View attachment 53313

See my Vacuum leak test in post #11 incl jowens126 HVAC Control Panel info & Mikey350 tests @ Help with dtc codes and idle
EXCERPTS:
When vacuum leaks are indicated, search out and correct the condition. Excess air leaking into the system will upset the fuel mixture and cause conditions such as rough idle, missing on acceleration, or burned valves. If the leak exists in an accessory unit, such as the power brake, the unit will not function correctly. Or Air Conditioning when in MAX mode may switch to Defrost.

&
One way to do a quick check is to grab a vacuum gauge. Some parts stores will loan you a gauge with refundable deposit.
The vacuum gauge should read between 15 and 22 in-Hg depending upon the engine condition and the altitude at which the test is performed. SUBTRACT ONE INCH FROM THE SPECIFIED READING FOR EVERY 1,000 FEET OF ELEVATION ABOVE SEA LEVEL.
The reading should be quite steady. .
When engine is rapidly accelerated (dotted needle), needle will drop to a low (not to zero) reading. When throttle is suddenly released, the needle will snap back up to a higher than normal figure.
 

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Registered
'96 Bronco 5.8L. 2.5" Tuff Country lift w/ extended radius arms, 33" Duratracs. Saginaw swap.
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33 Posts
Discussion Starter · #7 ·
Got a vacuum gauge and vacuum pressure is normal. Going to fuel pressure next I guess...
 

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Registered
'96 Bronco 5.8L. 2.5" Tuff Country lift w/ extended radius arms, 33" Duratracs. Saginaw swap.
Joined
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33 Posts
Discussion Starter · #8 · (Edited)
Yo truester.rooster,
I missed this thread!
yo J,
This is from 94 PCED (PARTIAL)
This 1994 Service Manual provides information covering Emissions for all 1994 Ford Motor Company Passenger Cars and Trucks except the 3.8L Mustang and 4.6L Thunderbird/Cougar vehicles which are covered in the Powertrain Control/Emissions Diagnosis OBD II manual. Complete emissions related diagnostic procedures for all affected systems or components are covered in this manual.
Diagnostic Routines Symptom Flow Charts — Chart 11 -
94 Surge Accel and Cruise View attachment 53313

See my Vacuum leak test in post #11 incl jowens126 HVAC Control Panel info & Mikey350 tests @ Help with dtc codes and idle
EXCERPTS:
When vacuum leaks are indicated, search out and correct the condition. Excess air leaking into the system will upset the fuel mixture and cause conditions such as rough idle, missing on acceleration, or burned valves. If the leak exists in an accessory unit, such as the power brake, the unit will not function correctly. Or Air Conditioning when in MAX mode may switch to Defrost.

&
One way to do a quick check is to grab a vacuum gauge. Some parts stores will loan you a gauge with refundable deposit.
The vacuum gauge should read between 15 and 22 in-Hg depending upon the engine condition and the altitude at which the test is performed. SUBTRACT ONE INCH FROM THE SPECIFIED READING FOR EVERY 1,000 FEET OF ELEVATION ABOVE SEA LEVEL.
The reading should be quite steady. .
When engine is rapidly accelerated (dotted needle), needle will drop to a low (not to zero) reading. When throttle is suddenly released, the needle will snap back up to a higher than normal figure.

Vacuum test
 

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Registered
'96 Bronco 5.8L. 2.5" Tuff Country lift w/ extended radius arms, 33" Duratracs. Saginaw swap.
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33 Posts
Discussion Starter · #9 · (Edited)
@truester.rooster add your Bronco details to your profile, that way we know exactly what we're dealing with..Year, engine/tranny combo and so forth.

Since you're getting a passing code 111, you might be staring at your answer here..

RANDOM OBSERVATIONS: Ever since I replaced my fuel tank and refused to replace the pump (years ago), the pump has whined super loud. I noticed today that when I'm sitting in my truck in park, while its running, if I apply the brake pedal, the pump whine gets quieter. Like its not working as hard? Or maybe receiving less power? Does this have anything to do with anything??

These pumps all whine to a certain extent but they will start to whine louder when they're on their way out..I'd start by checking your fuel pressure and then we can go from there. Don't throw any more parts at it until you do that.

For reference, engine running you should see 30 to 45 PSI, key on engine off 35 to 45.

Check out this link: Part 2 -How to Test the Fuel Pump (Ford 4.9L, 5.0L, 5.8L)

I should have listened to you from the beginning, Jermil- and checked the damn fuel pressure first thing... I believe I found my issue. Thank you for the advice! Think it's the fuel pump?

 

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126 Posts
Does the fuel pressure regulator hold vacuum? If not, replace it.
If the FPR is holding vacuum, run the fuel pressure test with the vacuum line off the regulator (plug the vac line also). It should be 39 psi.
If not then the pump looks weak.
 

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Charlie don't surf..
'92 Ford Bronco XLT
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16,089 Posts
At least you're closer to figuring it out..better late than never..as @Narve said, check the FPR, although my bet is that's ok..That's one of those parts that rarely fails in my experience, but still good to eliminate from the equation..looks like a pump issue to me.
 

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Registered
'96 Bronco 5.8L. 2.5" Tuff Country lift w/ extended radius arms, 33" Duratracs. Saginaw swap.
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33 Posts
Discussion Starter · #12 ·
At least you're closer to figuring it out..better late than never..as @Narve said, check the FPR, although my bet is that's ok..That's one of those parts that rarely fails in my experience, but still good to eliminate from the equation..looks like a pump issue to me.
Did some more fuel pressure testing... please watch my video. I'm really thinking it is the pump now. Wondering if I can do any other tests to solidify that diagnosis before dropping the tank.

 

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Charlie don't surf..
'92 Ford Bronco XLT
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16,089 Posts
It's running really rough, definitely sounds like it's starving for fuel..the fact that it's so low key on engine off and it's still below 30 psi with the engine running is a pretty good indication it's your pump..Haven't read back through the post, did you already pull the filter and replace?

Rather than dropping, you might want to consider just cutting an access panel if you have the tools. There are quite a few threads detailing the exact measurements where you need to cut in the bed and it's a bit of work, but it makes the job a whole lot easier in my book..

keep us posted.
 

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Registered
'96 Bronco 5.8L. 2.5" Tuff Country lift w/ extended radius arms, 33" Duratracs. Saginaw swap.
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33 Posts
Discussion Starter · #14 ·
It's running really rough, definitely sounds like it's starving for fuel..the fact that it's so low key on engine off and it's still below 30 psi with the engine running is a pretty good indication it's your pump..Haven't read back through the post, did you already pull the filter and replace?

Rather than dropping, you might want to consider just cutting an access panel if you have the tools. There are quite a few threads detailing the exact measurements where you need to cut in the bed and it's a bit of work, but it makes the job a whole lot easier in my book..

keep us posted.
Thanks for checkin' back in on me! I did replace the filter right before doing my first fuel pressure test, also dumped some seafoam in.... so should be running at its' best. I have dropped the tank before so I was planning on doing that again- but I will look more into the access panel first.

Now that I've hacked into the body so much to install the soft top etc. what's one more hole gonna do? Haha.

Thanks again.
 

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Charlie don't surf..
'92 Ford Bronco XLT
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16,089 Posts
you're welcome..If you've already hacked into the body, I'd say cut the access hole.
 

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Charlie don't surf..
'92 Ford Bronco XLT
Joined
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16,089 Posts
For reference..here's my rig, key on engine off, I've got an aeromotive adjustable FPR, they bleed down faster than a stock unit..It starts at 40 when I turn the key on then will drop to about 25..


Didn't get a video while running, but mine sits just over 40 PSI, the pressure is bumped up a bit because of the tune I run.
 

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'96 Bronco 5.8L. 2.5" Tuff Country lift w/ extended radius arms, 33" Duratracs. Saginaw swap.
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33 Posts
Discussion Starter · #17 ·
Hello folks! Figured I couldn't leave y'all in the dark.

Update: sold the '94 Bronco after acquiring my new '96 (less rust overall better condition).

Luckily the new owner of my '94 kept me updated when he took the Bronco to his mechanic. Turns out the main cause of my engine issues was the secondary air injection pipe (??). Also the shitting TPS I put on just f'd things up even more, so that was replaced again, I guess.

Apparently she is running smooth as can be! Never needed a new fuel pump!
 
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