2006 6.0 that randomly bucks, especially over 70 with cruise control on up hill. Changed oil many times, checked all my numbers, and even got a fass fuel system to try and help. No difference. Can anyone give me an idea on what it could be before I, start spending money changing the problem? Thank you.

 

Sounds like an injector dropping out. What's the FICM voltages?
Get the truck hot and do a bubble test. Pull the secondary fuel filter and crank it using the trigger wire on the passenger side near the fire wall. SEE PIC BELOW.
Unplug the bullet connector and when you touch it to the battery positive it will crank but not start. Crank it for 15 seconds while watching in the fuel bowl and see if you see bubbles. If you do or don't post your results.

 

Was running at steady 48 earlier today at idle. And will do thank you

 

Does it seem to buck warm/ hot or anytime cold start to hot ?, the ICP connection is known to short out during warm/ hot driving , with the engine running do a pinch wiggle test at the grey clip on the connection , to see if the engine acts up.also look for oil out the back of the sensor and inside the Connection.

 

Never really cruising at 70 unless on interstate. By then engine is already warm. But I will try making do it when it's cold. Thanks I'll try the connection also

 

Usually it will do it warm / hot as current and wires are warmed up , if it's shorting out , take the plastic grey clip that holds the 3 wire off and spread then open your looking for white spots on the wires , I'll see if I can dig up a picture

 

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for clarity you want to bubble test when problem is present

if it does hot bubble test hot
if does it cold test when cold