2004 8.1L Ticking/Rattling @ 1800 RPM

[recycleoldgrowth]

So my 8.1 has 130K, no mods. I'm the third owner, was sold to me out of Canada. Some good amount of rust on the undercarriage but nothing to alarming.

Recently I hear a loud Ticking/Rattle right at 1800RPM that will continue if I hold it there. I'm assuming it's on of two things, lose heat shield or exhaust leak. I'm also getting a noticeable ticking sound when I accelerate and let off.

I have also lost 2mpg. Rough idle as well. No codes. I'm going to put it up in the air this weekend to have a look but I'm here to ask for guidance as well. Thanks in advance.

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[barrrf]

manifold leak?

 

[Khaos]

manifold leak?

This. I'd check there first.

 

[recycleoldgrowth]

Would this also cause the negative Fuel Trim numbers I'm seeing? Wouldn't it be a positive number because the computer thinking it's got a lean condition? Thanks for your feedback.

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[Ginger]

yes, because it is letting air in before the O2 sensors causing false readings.

 

[recycleoldgrowth]

yes, because it is letting air in before the O2 sensors causing false readings.

So yes it should show a positive number with unmetered air getting in before the O2 sensor?

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