My 2006 6.0 has started what if it were gas engine I would call mis-fire. Even at idle it stumbles but normal powering down the road, it really runs rough.
I installed a new EGR valve, installed new dummy plugs and standing pipes but no change. Someone suggested that the T6 oil I'm using could be foaming and I should add anti-foamer.
Where would you look if it were your truck?

 

foam in oil I doubt that

Fuel filters been changed recent??

scan for DTC

Do you have a SGII???

Check FICM Volts

 

That is a symptom of a failed injector. Check your fuel pressure, install the blue spring (upgraded fuel pressure regulator spring) if you don't already have it, and do a contribution test to see which injector is failing. A failing injector won't throw a code or light the check engine light.

Brian

 

That's not true. Depending on the severity of it, it may not throw a code, but all the failing injectors that I've seen have thrown a contribution/balance code.

Now you are right that it won't lit up the CEL, but it can throw a code.

 

Normal power when running? I would think ICP.

 

I vote for bad injector.

In my experience, a bad injector may not throw a DTC. Ford has the contribution balance dialed way back on these engines, probably because if they didn't, cold start stiction would be setting codes to the point of nuisance. When it gets bad enough it will fault, and if it fails electrically it will definitely fault, but it can be sticky enough to feel like a miss without a DTC. Running a contribution test with a graph will show what is really going on.

 

On codes - I've lost three injectors, at three separate times in the space of a week, in my 6.0, due to low fuel pressure. None "threw a code" - put out a code that could be read with a simple, plain jane code reader. All did fail a cylinder contribution test with a more sophisticated computer than a code reader. Failing a cylinder contribution test would seem to me to be different than setting a code, but I don't know...

My theory is that running with low fuel pressure under a high load will cause sort of instant stiction, or something like that. My truck had exactly the symptoms noted by the OP, no codes set that could be read with a normal code reader, so that's the basis for my guess...

Edit: FWIW the first time mine failed, I ran another 100 - 150 miles after the first symptom and it stranded me, wife, cat, and trailer and had to be flat-bedded 50 miles to a dealer for service. They changed the first injector, and didn't diagnose the low fuel pressure. The truck basically lost all power, would barely start, no idle, and would move at 10 mph tops after sitting for an hour each time. The second and third time I was able to drive off the highway, maybe 15 miles tops. and didn't get stranded. Dealers being dealers I had to wait three days each time to actually get in a bay, each injector cost $1,000 to have changed, and I got a weeks vacation while I waited in motels for it to get fixed each time... At the end of the day it got transported back to the selling dealer, who replaced all 8 injectors, the HFCM and installed the blue spring...

Brian

 

Let me reiterate this. It may or may not throw a code, it depends on the severity of the issue, however, you can get codes that are "cylinder contribution/balance" codes. Those are codes, not the same as the contribution test that bpounds is talking about.

I'm not saying that it will always throw a code, but there are codes there.

As to your plain jane code reader, that isn't going to do you a whole lotta good with the 6.0. It costs you less in the long run to get a decent code reader then to cheap out. Just because your code reader isn't good enough to get into the more specific codes, doesn't mean that the truck isn't throwing those codes.

 

I think I agree with Tex.

A contribution test is a contribution test, no matter what tool is used. A contribution test senses how much each cylinder firing is "contributing" to each crank cycle. It compares each cylinder firing to the average of all cylinders. The PCM is running the contribution test at all times, and if a cylinder is contributing xx% more or less than the average, a fault is indicated. The question is, at what percentage is the fault indicated. This is an engineering decision.

IMO, they have set the margin pretty loose on these engines, and you can easily feel a slight miss before the PCM considers it a problem. That was my point.

That same contribution test run on IDS or Autoenginuity for example, will show a graph with the percentage above or below average shown for each cylinder. The technician then evaluates that data. It's the same test, and in fact it is using the same PCM data. Just showing you in graphical form so you can make your own determination.

This is how I understand it, but I can be wrong.

 

You got it right, at least how I have it worked out in my head as well.

 

That's what I wanted to learn, so thank you for explaining that. It makes sense that the PCM puts out codes for the cylinder contribution. My confusion was the difference between the PCM setting code alarms based on passing a threshold, vs asking for the code data on the basis of a test.

Brian