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P0442 and P0456 codes

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Old May 17, 2026 | 01:42 AM
  #1  
HankMurphy's Avatar
HankMurphy
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From: SoCal
Unhappy P0442 and P0456 codes

2008 XL regular cab with 4.2L V6 and automatic. 205000 miles. A couple of weeks ago I got a P0104 code with a CEL. Cleaned the MAF sensor and it ran OK for a few days.

But now I am getting P0442 and P0456 codes. I’m thinking new plugs, coils, and plug wires may be the fix. Plugs are old. Motorcraft Platinum plugs were suggested in another thread. But before I start throwing parts at it, what else should I be looking at first?

Symptoms: Regular stuttering and shuddering going up hills at 60MPH. Not much at lower speeds, although steeper hills at 25-35 MPH have the symptoms too.

Codes are read with a ScanGauge I.

i’ve seen a few posts where people recommended first replacing the gas cap for emissions codes. But I went to order a new gas cap and Ford is out of stock per dealer parts department. Any ideas of a replacement part source?

Thanks in advance for any advice!
 
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Old May 17, 2026 | 06:48 AM
  #2  
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techrep
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From: Virginia Beach
you can buy gas caps anywhere, Amazon has them... any DTC's or a flashing Check Engine Light CEL when shuddering? have you checked the FPDM yet ? When was the last tune-up ?
 
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Old May 17, 2026 | 11:27 AM
  #3  
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HankMurphy
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From: SoCal
@techrep thanks for your comment! Yes, CEL is on.

This is a 4.2…does it have an FPDM? The FPR indicator on my ScanGauge stays blank - no signal. Linear Logic didn’t respond to a question I asked their tech support about that, so it may just not be there. But I should probably change the fuel filter too, and maybe have the fuel pump tested?

Edit: I stand corrected, looks like it does have an FPDM. Any further testing I should do before firing the Random Parts Cannon?
 

Last edited by HankMurphy; May 17, 2026 at 11:44 AM. Reason: Wrong info in response.
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Old May 18, 2026 | 06:07 AM
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techrep
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From: Virginia Beach
remove it and check out the back side, they love to split open do to corrosion and cause problems. Do you have a way to retrieve the codes from the CEL ? auto zone or advanced will read them from free.
 
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