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Powerstroke Tech
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Discussion Starter · #1 · (Edited)
ive had a p0278 for a while now, which is cylinder 6 contribution code:

Diag preformed:
using ford ids
-powerbalance- cylinder 6 only drops out slightly (not even -20) on a hot engine only while in gear at a dead stop.( rpm raised to 900 while power braking power balance smooths out.
-relative compression- no compression loss on all 8 cylinders
- manual compression test- 450 psi on all 8 cylinders

Parts replaced:
- #6 injector
-#6 injector cup
- cylinder 6 pushrods
-cam shaft ( cylinder 6 exhaust lobe lift was 5,000ths less than a good cylinder)
-all lifters.
-head gaskets, and all gaskets required to remove and replace heads.
-arp studs
-driver side cylinder head
- valves
-springs
-valve guides
-regrinded the seats
-pressure checked
-injector harness
-swapped pcm
-injector in cylinder#4
-icp sensor and connector
-cam sensor
-fuel pump
-fuel pressure regulator( blue spring)
-ipr

Ficm is good, batteries recently replaced as well.


Has anyone came across this issue or any ideas to the cause?
 

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wow you've got a good one there.

when you say FICM is good have you actually replaced it or tried a known good one? A ficm can cause individual cylinder concerns and while rare, I have personally seen it. A tester ficm is invaluable

I'd start looking at the FICM or ficm harness first. Obviously the harness was out of the vehicle to do headgaskets and I assume nothing unusual was noted about it.

Other than that nothing really stands out about #6.
 

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You're lucky it is only 20 psi low. I had the same code (plus a couple others) and my manual compression test was 100 psi low...ended up getting a new short block under warranty. We have different motors though...I'm not really sure what I'm getting at here.
 

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Actually what the OP means is the RPM drop during idle is less than 20 RPM on that cylinder.

A low contributing cylinder is easily identified with a ford IDS by how much the engine slows down whenever a particular cyl fires.
 

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X2 on the FICM...I had a cyl 4 cont. fault and a dead miss at idle. Chased it kinda like you did. Replaced injector 3 diffrent times, replaced harness, hold down, and all the standard compression tests and fuel pressure tests. Finally I swapped a buddys FICM in and bamm. No more miss or contribution code. Passes a power balance test with flying colors. I had a rare logic side faliure in the FICM.
 

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Powerstroke Tech
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180 Posts
Discussion Starter · #6 ·
I replaced the ficm with a known good one, but that was before the cam was replaced. when vieweing power balance the rpm doesnt really change rpm. The part that keeps throwing me off is that the mis only happens on a hot engine. Whens its cold after sitting the powerblance is smooth with no drops outs. once the temp guage moves cylinder 6 slowly starts droppping out.
 

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possibly a bad oil solenoid/leaking on that cylinder? Was the actual compression any different on that cylinder. I have seen pistons where the ring gaps all line up allowing a slight loss of compression and cause a miss. There is no damage or visible signs when you look at the cylinder it is only found by looking at the piston itself out of the truck.

One of those last resort things.
 

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Powerstroke Tech
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Discussion Starter · #8 ·
Ive done manual compression and relative compression numerous times, each time showing no loss in compression and all cylinders have the same compression. I ordered 4 valve springs today, going to try to get them in this week. If that doesnt work my buddy has a truck i can take parts off of ( ficm and harness). I cant really see it being a ficm or harness since its a conrtibution code not a circuit high/low code. Ive also been told by ford hotline it could be a slightly bent crank sensor tooth. Cant see that being the cause if the mis is only present on a warm engine.
 

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considering the problem occurs once it warms up, the parts replaced so far, and compression readings all checked out, it sounds like an electrical issue. either the harness or ficm. since you say you've tried another ficm, i'd try the harness.
it may not throw a circuit code since it's still electrically operating within the pcm's expected range
 

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Powerstroke Tech
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Discussion Starter · #10 ·
I changed both the ficm and the injector harness today. no difference cylinder 6 still drops out. Also did a cylinder leak down test with the engine cold had no leak down. Going to try it with a hot engine tomorrow see if there is any difference. The only things left are valves/springs, piston rings, and pcm but that seems like a long stretch due to the effect engine temp has on it.
 

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For grins swap the new cyl 6 injector to 4 or 8. Retest. Just had a new injector out of the box do the same thing to me thos week.
 

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Powerstroke Tech
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Discussion Starter · #12 ·
Already put 4 injectors in that cylinder odds are its not an injector.
 

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My bad...must have missed that part. Well with that info and the parts you replaced I think I would be trying a pcm next for grins. This is a good one for sure...I would like to know what fixes it.
 

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Man I'm trying like hell to think up an answer for you but nothing's clicking yet. I know it's nice to have a second opinion on things like this.

So you didn't get the valve springs in yet? I'm interested to hear what you find there
 

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Powerstroke Tech
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Discussion Starter · #15 ·
I haven't had a chance to put the spring in yet. Got Buried this week at work so far between head gaskets and drivability stuff on customers trucks. Hopefully I will have some time to pull my truck back in tomorrow. Only had the chance to swap the ficm and harness no luck there. One if the guys i work with got a chance to talk to a ford engineer last night after I left. He said try putting springs in. My worry is that the valve is sticking or binding when opening and that's why the cam love was off in this cylinder. Was going to try to change the springs with the head still on the block. Debating on pulling just that side off and changing valves and guides too. Just that's a lot of down time.
 

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Powerstroke Tech
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Discussion Starter · #16 ·
Finally got around to pulling the head off. Took all cylinder 6 valves out 3 out of the four valestems where worn on one side and not the other and had a lot of play to them. Measured the vale spring heights 3 where 52.33 mm. One was 52.17 mm. The valve seats where all pitted. Sent the head out to the machine shop as well. See what they have to say. Having them install all new valves and spring in cylinder 6. Hopefully this is my issue.


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Powerstroke Tech
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Discussion Starter · #17 ·
Head is at the machine shop. They said the valve guides were wasted. Iam jut waiting on them now the send the head back to me. The reassemble and see what happens.


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Have a similar problem with mine, went and had a leak down done and it's an intake valve, heads coming off then studding in the works for me
 

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Powerstroke Tech
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Discussion Starter · #19 ·
Wish I was Able to say the same. The head was shot. Got it rebuilt put it all back together. Code came back within twenty minutes. Only thing left now is the PCM and the crankshaft tone ring.


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Well so much for that being simple...looks like something as well as the valve scored the piston pretty good...any thoughts on where to go from here?

 
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