Catalytic Converter?
Posting Guru
Joined: Oct 2005
Posts: 2,209
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From: Louisville, Kentucky
There is a very good, but lengthly thread on that code. Read through it and I'm sure you will find a solution there. Good luck! 
https://www.ford-trucks.com/forums/248921-diagnostic-code-p0401-insufficient-egr-flow.html
https://www.ford-trucks.com/forums/248921-diagnostic-code-p0401-insufficient-egr-flow.html
Freshman User
Joined: Jan 2008
Posts: 36
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I had this same problem on a Chevy Z-71 pickup that I owned way back before I switched to Ford. (no need for any Chevy haters to send me emails)
Anyway, I had the loud rattling sound, at idle, that you appear to be experiencing.
I allowed my exhaust system to cool then I crawled under the truck and started banging on different areas of the exhaust system. I just hit these areas with my fist, but I think a rubber mallet would work just fine.
I was carefully listening for any loose connections, vibrating parts, etc.
When I hit the cat. convertor it rattled and sounded like bits and pieces of something were broken off inside of it.
I took the truck to the muffler shop. They cut off the old cat and installed a new one.
The mechanic brought the old cat to me and shook it. It was rattling like crazy.
Anyway, I had the loud rattling sound, at idle, that you appear to be experiencing.
I allowed my exhaust system to cool then I crawled under the truck and started banging on different areas of the exhaust system. I just hit these areas with my fist, but I think a rubber mallet would work just fine.
I was carefully listening for any loose connections, vibrating parts, etc.
When I hit the cat. convertor it rattled and sounded like bits and pieces of something were broken off inside of it.
I took the truck to the muffler shop. They cut off the old cat and installed a new one.
The mechanic brought the old cat to me and shook it. It was rattling like crazy.
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Former ******
Joined: Nov 2004
Posts: 4,901
Likes: 2
From: Salt Lake City, Utah
I had this same problem on a Chevy Z-71 pickup that I owned way back before I switched to Ford. (no need for any Chevy haters to send me emails)
Anyway, I had the loud rattling sound, at idle, that you appear to be experiencing.
I allowed my exhaust system to cool then I crawled under the truck and started banging on different areas of the exhaust system. I just hit these areas with my fist, but I think a rubber mallet would work just fine.
I was carefully listening for any loose connections, vibrating parts, etc.
When I hit the cat. convertor it rattled and sounded like bits and pieces of something were broken off inside of it.
I took the truck to the muffler shop. They cut off the old cat and installed a new one.
The mechanic brought the old cat to me and shook it. It was rattling like crazy.
Anyway, I had the loud rattling sound, at idle, that you appear to be experiencing.
I allowed my exhaust system to cool then I crawled under the truck and started banging on different areas of the exhaust system. I just hit these areas with my fist, but I think a rubber mallet would work just fine.
I was carefully listening for any loose connections, vibrating parts, etc.
When I hit the cat. convertor it rattled and sounded like bits and pieces of something were broken off inside of it.
I took the truck to the muffler shop. They cut off the old cat and installed a new one.
The mechanic brought the old cat to me and shook it. It was rattling like crazy.
There are 4 converters on most F-150s, a front pre converter, and a main converter. It is more common for the pre converters to break apart and get blown back into the rear converter, but if this was the case, you would probably be experiencing a severe loss of power.
With your code, I suspect you need to clear out all the EGR lines and replace the EGR sensor.
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Freshman User
Joined: Jan 2008
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That's why I suggested allowing the exhaust system to cool then crawl underneath and started lightly banging on everything to see if the cause of the rattle could be found.
It very well could be a loose heat shield.
I was just telling the original Poster about the cause of the same rattling problem I had that he is experiencing.
It very well could be a loose heat shield.
I was just telling the original Poster about the cause of the same rattling problem I had that he is experiencing.
Senior User
Joined: Dec 2005
Posts: 348
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From: Hemet, California
It does happen though, had to have the driverside (both) replaced cause I broke everything loose inside. And BearRiver isn't joking about the loss of power. How I managed it is beyond me as it was before I set it up for and started taking it off road. Had them replaced and good as new
Freshman User
Joined: Jan 2008
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Oh, yeah. It definitely happens regardless of what model truck you drive.
I didn't experience any loss of power though. I guess when my cat fell apart it wasn't as bad as what it could have been.
But, it sure made a racket.
I didn't experience any loss of power though. I guess when my cat fell apart it wasn't as bad as what it could have been.
But, it sure made a racket.
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