[IQRaceworks]

I've had an intermittent problem with my 05' 6.0 F250 for a while now. If I'm on the highway in high gear with the convertor locked in, cruising around 70mph at 2,000rpms.......if I smoothly roll onto the throttle so that the transmission doesn't kick down or unlock the convertor, as the boost starts to build......the motor starts to shutter/stumble and shake a little bit, it almost feels like a misfire. Now if I hit the pedal fast enough where the transmission will kick down a gear, it runs like a top...nice and smooth, full power with no issues.

The only time it does the stumble/shutter/misfire type thing is when I really bog it down, in high gear, with lots of boost (27psi).

I have no codes, HPOP pressures are good (580 idle/4,100 at wide open throttle). Fuel filters are all clean, and overall the truck runs like a top. I'm running a mild IDP towing tune.

I surfed some of the facebook 6.0 forums....and I had people telling me it was a bad HPOP, or ICP, or cracked head, or low fuel pressure, or bad fuel pump, bad torque convertor, or "it's normal to do that".....

The only thing that really makes sense to me is that it might be a weak injector that starts to crap out under big load.....does that sound plausible.

Any ideas on where to start troubleshooting this? No codes, so I'm starting from nothing. Maybe a cylinder contribution test?

 

[Jax]

Welcome to PSN!

I'm not into 6.0L, but I am sure someone will be along shortly!

 

[matthewd11]

Likely injector stiction.

 

[IQRaceworks]

Likely injector stiction.

Any idea on what it would only happen under a really big load at lower rpms? At high rpms it runs like a top.....and even cold starting when stiction is uslaly evident, it's fine.

I was just curious.

 

[matthewd11]

The spool valve can stick with ICP pressure is high and relatively “low” rpm under converter lockup. At higher RPM and converter unlocked ICP pressure is also lower. It’s pretty common to happen the way you describe in addition to cold starts. A poorly operating FICM also can make stiction appear worse, especially when cold.

If you slow to 60 mph and slowly ease into the throttle you’ll be able to get it to act up and it will be more noticeable than close to 70 mph.

 

[IQRaceworks]

The spool valve can stick with ICP pressure is high and relatively “low” rpm under converter lockup. At higher RPM and converter unlocked ICP pressure is also lower. It’s pretty common to happen the way you describe in addition to cold starts. A poorly operating FICM also can make stiction appear worse, especially when cold.

If you slow to 60 mph and slowly ease into the throttle you’ll be able to get it to act up and it will be more noticeable than close to 70 mph.

Makes total sense!! Thanks! I guess since I'm not getting any codes, the only way to tell which injector(s) are sticking is to take the truck somewhere and have a cylinder contribution test done...right?

 

[matthewd11]

Yes, but that still may or may not be definitive. You may have to wait until the PCM blames a specific cylinder. I would also verify your fuel pressure is what it needs to be.