Strange miss at idle

[LHMissions]

Alright. So to date (since factory head gaskets/ factory bolts failed in October 2009 with 199,700 miles) - I have had completed a:

• new Motorcraft headgaskets
• milled and magnafluxed heads
• headwork done, new valve seats and seals
• ARP studs
• new oil cooler
• new radiator
• egt probe in driverside exhaust
• new 4" turbo back Diamond-eye Exhaust with kitty delete
• full DIY EGR delete
• 8- new Motorcraft glow plugs
• new Motorcraft Glow plug harnesses
• new IPR (original had screen clogged and had 199,700 miles - time for new)
• all top end O rings and gaskets replaced with new
• new serpentine belt
• 1 new injector

As of today - she starts and runs right away - fires right up. The new exhaust sounds sweet! But there is a problem.

There is a miss on cylinder #4. Originally thought was a bad injector so replaced this injector (hence the "new" injector in list above)

Didnt solve problem.

I'm getting code P0272 - Cylinder contribution fault
Cylinder #4 (when we first got this code - we replaced the injector with new thinking it would fix the problem. New injector and we still have the code)

Injector 4 was put in #4 slot and replaced all O-rings and compression ring.

Passes buzz test and can disable #4 injector through solus scan tool and no engine change. All others draw down engine when disabled.

When lightly reving engine - no more then 500rpm rev - there is a noticible clicking that increases and decreases with the rev of the engine. At base idle its not evident there is a click sound. Could a lifter or valve be stuck?

Other engine notables. When heads were off - cylinders were clean and nearly new. Seals were good and no visible damage. Cross hatching was excellent.

Any ideas. We need some help here guys. The injector has oil pressure and fuel. The injector functions and you can hear the buzz and click so the FICM should be functioning correctly, right? I mean - it passed the buzz test.

So where do we go now?

[bigcountrysg]

I would suggest you pull the injector and have it bench tested.

[sportsman500]

you have lost compresion in that cylinder , do a manual compression test to verife . i've run into this before , turned out one of the exhaust valves was damaged do to something going though it .

[dannyboy950]

I agree check for compression loss on that cylinder.

[LHMissions]

What compression psi are the cylinders supposed to hold? So I know.

Thanks and Merry Christmas Everyone!!!

[LHMissions]

IF it is a compression loss on that cylinder - not knowing where the loss is occuring - what options would there be to correct or is this question too premature?

The piston seals were good, the walls of the cylinder were clean and no visible or finger felt scoring or damage visible. Heads were magnafluxed and found without fault. New valves seats & seals. what else would it be?

[dannyboy950]

A valve could have gotten bent and is not closeing all the way. A spring may have broken allowing a valve to not seat correctly.
Check the compression on all cylinders at least on that side, #4 should be considerably lower than the others if that is the problem. Drivers side front to rear 2; 4; 6; 8

A diesel compression gauge will be needed and an adapter to screw in the glow plug hole both available from any OTC tools dealer.
A good tight cylinder can give from 300 to 400 psi of compression so a standard automotive tester wont work.