5.4 engine problems
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1st Gear
Joined: Nov 2024
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5.4 engine problems
My 2009 ford f250 super duty with a 5.4 is making some pretty strange sounds. To start, it is showing p0191 and I think the other code was something “tracing back to the cidilidic converter”. When the truck starts cold, it sounds fine. But once the engine is running at operating temperature it makes a weird clown horn sound. The sound only occurs when I let off the gas or when it is idling. Then when I put it in park it will start surging while making the noise. When I turn the truck off, it will make a long sad clown horn sound like it is loosing some kind of built up pressure. I took it to my local ford dealer for a brief moment and no one could tell what it was on the spot. I just recently bought this truck and the previous owner said the noise started a week before after he had gotten it detailed. Mind you, when I saw it for the first time it was recently undercoated and sprayed, and the engine was covered in wd40. The bed of the truck also was replaced and it was converted from flat bed, back to original bed. The fuel gage is also stuck on max full at all times while running. The gas pump automatically turns off every time I press down. Not sure if that’s related. Any advice will help. Thank you
Fleet Mechanic
Joined: Dec 2003
Posts: 1,436
Likes: 117
From: Virginia
If I had to guess, the fuel pump issue was likely caused when they swapped a bed back on.
Someone probably damaged wires on top of the tank.
The issue you are describing “sounds” like there is a build up of pressure in the exhaust caused by failed catalytic converters.
This is a fairly common issue when an owner doesn’t address a drivability/ engine issue & it fouls the converters.
Does it feel under powered?
When you put the pedal down does it bog down or feel like it isn’t responding like it should?
It can be hard to diagnose a fouled converter, but a good test would be to watch the temp on the converters.
if you have a scan tool you can watch live data & see what temp they are running.
Startup should be 700-800deg. Fully warmed up should run around 1200-1400deg while driving.
If you are seeing temps higher or lower than that, there is a good chance they are not flowing correctly
I replaced mine a few years back after fixing a lot of issues & it woke the #$&*@ up like crazy.
Someone probably damaged wires on top of the tank.
The issue you are describing “sounds” like there is a build up of pressure in the exhaust caused by failed catalytic converters.
This is a fairly common issue when an owner doesn’t address a drivability/ engine issue & it fouls the converters.
Does it feel under powered?
When you put the pedal down does it bog down or feel like it isn’t responding like it should?
It can be hard to diagnose a fouled converter, but a good test would be to watch the temp on the converters.
if you have a scan tool you can watch live data & see what temp they are running.
Startup should be 700-800deg. Fully warmed up should run around 1200-1400deg while driving.
If you are seeing temps higher or lower than that, there is a good chance they are not flowing correctly
I replaced mine a few years back after fixing a lot of issues & it woke the #$&*@ up like crazy.
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