Ok I've been having a problem with my truck. It seems to only happen when she is in regen. And only when it is running up hills . If you can call them hills here in Florida. the truck will start to buck like a miss fire in a gas eng. It only happens when you roll on the thottle slowly. When it starts to miss the noise from the eng will get louder. The dealer doesnt know whats causing it. I've changed fuel filters and where I buy fuel.Any help would be great .

Thanks

 

You're not the first one who's mentioned bucking, but I don't remember what caused it.

Any smoke coming out of the tailpipe? Most of Florida is pretty humid, and the 6.4L trucks have problems with water accumulating in the CAC during part-throttle operation, and then when boost comes up it gets blown into the engine causing misfiring. Of course the 6.7L doesn't use the same CAC design so I think it's unlikely.

 

Mine does the same thing. It seems to do it mostly at lower rpm and when I force a downshift it seems to help. It did it yesterday at 70 mph but not as bad as usual. I asked my brother if he felt it and he said yeah my truck does the same thing.

I'm trying to set an appointment with the dealer this week for several other small issues and this is on my list. My truck has not been reflashed since it left the factory last October so I was hoping that maybe the latest flash would help that. It will be interesting to hear from others what their experience has been.

 

Is it possible to have an injector issue without a CEL lighting up?

Air filter in good shape?

I had similar issue with my 6.4 under heavy load during regen and I believe it was caused by the CAC but ours on these motors are vastly different and I have not felt the "stutter" sensation with this truck.

Long list of components working during a regen, lots of sensors, turbo vanes, EGR valve, injectors. I would not know where to look first and/or how. Air and fuel delivery is crazy technical.

 

Mine does the same, I always thought it was because the truck is always in too high of a gear IMHO and does not want to down shift until you give it some right foot. Seems like more transmission than engine at least for me. At just over 40 MPH my truck is in 6th, if I roll on the throttle slowly it does not down shift and starts to buck. I hear a weird noise from the trans (like if you throw a band saw blade on the concrete floor, don't know how else to describe it). For this reason I usually drive in tow / haul unless I am on the hiway. H&S trans tuning made this worse so I am back on stock trans tune.

Thanks

 

Just for clarification, my truck is in active regen when this happens. I never noticed the problem when a filter cleaning is not happening and it only seems to last a minute or two at the beginning of the regen cycle.

 

Mine is definately not in active regen when this happens.

 

I have this problem occasionally, but only when the engine is cold. Seems like the engine dies for a split second then takes off again. this is a 0-5 mph with slow acceleration. I do notice a little sliggishness when rolling into the throttle, but in my experience, diesels have always done that a little - at least my '05 did.

 

Mine is bucking occasionally as well. It first appeared after the latest ECM update along with sluggish shifting and a few seconds of loss of power at full-throttle up-shift (accelerating).

The bucking seems to happen mostly at low RPM (less than 1600) with light throttle. So far, it never happened when in regen. It typically happened shortly before a regen cycle started (I am using an Insight CTS watching the soot accumulation value so I know when a regen is about to start). -- NO CODES when any of this happens!

I changed fuel and air filters - same deal. One time the engine actually stalled after bucking for a few seconds in city traffic. Turned off ignition and re-started the engine and it worked OK after that. This time I did get two codes: 1 related to the crankshaft position sensor and the other related to the fuel rail pressure sensor (signal high - as in temporarily disconnected). Ford replaced the crankshaft position sensor. However, the engine did buck twice since that repair. I pulled and re-positioned sensor connections and all three ECM connectors. I never saw the fuel rail pressure sensor code again, but continue to get the occasional bucking.

I wish there was a way to restore the prior ECM code. The engine had more power and never exhibited this kind of problem.

 

I have had this happen to me also. At the time I was towing a 5th wheel trailer and was site seeing, going very slow, and did not have tow/haul on. RPM was below 1000. The transmission seemed not to shift down. I would push tow/haul and give it some throttle and it seemed to run right then. This has happen two or three times. I thought I was just lugging the engine at low RPM. Never had it happen when not towing.

 

Mine is doing this as well. It feels almost like something cutting fuel to the truck intermittently....kind of a surging feeling. And it only happens when it's in regen.

 

It would be nice to know what causes it, but I'm glad to know that I'm not the only one! I wonder if Rick's truck did this prior to the HPFP failure?

 

Does the bucking correlate to the bulge in turbo PSI consistent with the active regen cycle? Do you notice any difference in the turbo PSI bulge during the "bucking" and when it is not bucking?

 

Do you guys hear a clunk (as I describe it) when this happens?
I was thinking transmission related but I don't really know.
I blamed it on transmission because that's the only screwed up part of my truck.
Feels like it downshifts then upshifts all within a second.

Mine is at slower speeds though; 3rd or 4th gear.
Happens when coasting then accelerating lightly but it's rare.

 

I have heard of people having boost fluctuations during regen, but I haven't noticed that. It just acts like it's missing and sounds like a gas engine with detonation.