Cylinder 6 contribution

[whitestrikr21]

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?

[sinner6.0L]

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.

[fordpwrstroke7]

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.

[sinner6.0L]

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.

[toren302]

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.

[whitestrikr21]

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.

[dannyboy950]

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.

[whitestrikr21]

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.

[kaya@bernhausen]

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

[whitestrikr21]

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.