Specs. 2008 F150 Lariat 5.4L 3V
295,000 miles


having a hard time deciding on whether it’s a COP, loose spark, cam phaser/roller, exhaust manifold leak?

Based on this sound being most audible from underneath the engine, wondering if there’s someone with a better idea of what to try first based on following the noise.

 

Sounds a bit like an exhaust leak, in combination with other general engine noise.

 

Sounds like a phasor lock pin to me.

 

Is chain slap on the list?

 

You do know you can use a shop vac on blow to look for exhaust leaks . You can even add smoke for a more visual indication . Look on you tube .

 

Exhaust leaks are easy; feel around with it running, you'll feel the air pulsing out. There will also be soot around the manifold mating joints.

Loose spark plugs are easy to check for; put a torque wrench on them and put them to 28 ft-lbs.

If those check out, I'd look at the followers; it sounds a tad higher pitched than the usual phaser knock, but could be video/computer effect on sounds. Either way you'd have to start pulling parts. Whether followers or phasers, however, they'd both be replaced at that mileage (which is impressive, btw). Whether or not it's worth it to sink $1400 in parts to a 300k mile engine is up to you.

 

sounds exactly like my 04, i think its an exhaust manifold leak on the passenger side, ive learned to live with it since the computer isnt throwing codes and the studs are old.