2004 Ford F-150 4.6L... wtf?

[Benshooter]

Alright I'll make this as short as possible. I just picked up this truck with the 4.6 2 valve head V8 and it's already got me stumped.

Truck has 80K miles, decent service history.

I was getting misfires at idle that would get worse under load but clear up after 3k rpms. After fuel, air, and spark checked out, compression came back low on cyl #2 and #5. I did a simple leak down test with 100 psi and got a lot of audible air coming out of the intake.

Wtff? Is it really possible that the valve seats are failing this early? I've seen plenty of burnt exhaust valves but never really had any problems with intake valves on engine with these miles... Could I be missing something obvious? I have the valve covers off so I can make sure the valves are not in phase on the cylinder I'm testing. The truck shows a decent amount of sludge in the engine. Nothing too alarming, but it's there.

Help me peeps.

 

[proteusx301]

I just went through all the TSB's for the Heritage 04 and new body style 04. Couldn't find anything like what you are describing and I can't seem to recall ever seeing that kind of problem with the 4.6 2-valve. If you dropped a seat, then you would be hearing the pieces in the cylinders. Are the valve springs or follower's damaged in any way?

 

[Benshooter]

Yeah I couldnt find any TSBs for it either. It's a heritage. Retired work truck.

Not that I can see. I'm working on getting the intake and front cover off now so I can pull the tensioners, cams, etc and get a better looks at the valve train. I'll check back in an hour or so with my findings.

Thanks for your help.

Alright so I pulled off the whole intake (damn thing must have weighed 60lbs) and the #2 intake port was CAKED with sludge, carbon, or some kind of black mess. I'm thinking the valve guide/seal is toast on that one and I'm PRAYING that all that gunk is preventing a seal.

Any more ideas?

Update: I soaked the intake ports in purple power overnight. All the valve seats are seating properly as far as I can tell.