Truck "bucks" at slow, steady speeds

[khyros]

What's your drive habits like? If you do a lot of short trips, or extended idles, the spark plugs could be fouled. You can clean them out with about 10min of high RPM driving (use manual mode to keep it in like 2nd gear).

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[THEMIZE]

My truck does this as well but only in my neighborhood(25mph) going up hill. I currently have a brand new loaner from FORD due to the blend door failure on my truck and it also does this same thing in same spot every time, vibrates/bucks more in the loaner IMO. I also had the TSB done on my truck at 12k miles.

My Truck:
2019 2WD XLT
21,500 miles
Stock(except the damper )

Loaner Truck:
2022 4WD Lariat
120 miles
Stock

 

[JohnnyO]

Could the transmission be hunting for the "right" gear? Seems like my truck wants to go to the highest possible gear all the time for better fuel economy.

Agree, trans may not be able to decide what gear to be in. Put it in Sport Mode and see if it does the same thing. If that seems to fix it, disconnect the positive battery cable for 15 minutes to reset the computer.

 

[FX4Offroad]

What's your drive habits like? If you do a lot of short trips, or extended idles, the spark plugs could be fouled. You can clean them out with about 10min of high RPM driving (use manual mode to keep it in like 2nd gear).

Short trips during the week. 15 minutes to work each way. Weekends lots of high speed driving... 3 to 4 hour highway speeds... 70+ mph.

Could the transmission be hunting for the "right" gear? Seems like my truck wants to go to the highest possible gear all the time for better fuel economy.

I watch the gear display when it's happening and it's not moving thru the gears. I've set to "Drive", '"Sport" and "Tow" modes and it doesn't stop the bucking. This is why I believe it's not the tranny.

 

[YaBoiNewton]

I have something similar, but worse. My idle is VERY uneven. Hunts from just under 1000, to 500 or so. Only at idle, or very light loads, like 20-30 mph, not accelerating or decelerating. Maybe one cycle per second, and it's not consistent. Occasionally stalls the motor when it drops too low. Dealer has looked at it twice, without resolving anything. They had no loaners available, so I've just been putting up with the annoyance. It runs normally, except my gas mileage is low (about 14-15 mpg...). Anything but idle is ok.
I've been suspecting a problem with the PFI injectors, as they only come into play at low load and idle, and I'm about to start another round of troubleshooting with the dealer.

Holy shit dude if you're getting that kind of mileage your truck is not running normally and there are some serious drive train inefficiencies going on there. Maybe not "serious", but that is not normal. If you're not under warranty maybe go to an independent mechanic to check it out. Try to be nice since these guys work hard, but definitely don't just put up with it!

Not to hate on dealer mechanics, but from what I understand it's a tough place to work so skilled mechanics tend to not stick around. Every dealer mechanic I've spoken to is overworked probably to avoid being underpaid. Further confirmed by both my boss and former mentor, both of whom were Ford master technicians before getting fed up and becoming engineers.

 

[Yinzcity]

Short trips during the week. 15 minutes to work each way. Weekends lots of high speed driving... 3 to 4 hour highway speeds... 70+ mph.


I watch the gear display when it's happening and it's not moving thru the gears. I've set to "Drive", '"Sport" and "Tow" modes and it doesn't stop the bucking. This is why I believe it's not the tranny.

Is your issue similar to what is discussed in this thread?
https://www.ranger5g.com/forum/threads/bucking-surging-epidemic.14581/

There's a realtively inexpensive part replacement that might help with the issue.

 

[NotBudule]

I watch the gear display when it's happening and it's not moving thru the gears. I've set to "Drive", '"Sport" and "Tow" modes and it doesn't stop the bucking. This is why I believe it's not the tranny.

If your at 25 mph , and it starts doing it , then you check the gears and it's in say 5th and you are at say 1300 rpms , then you pull it back in sport and nothing changes ? It should immediately rev up and downshift , tow will a little, sport alot...

 

[FX4Offroad]

If your at 25 mph , and it starts doing it , then you check the gears and it's in say 5th and you are at say 1300 rpms , then you pull it back in sport and nothing changes ? It should immediately rev up and downshift , tow will a little, sport alot...

I'll try that. Thanks

 

[FunInTheSun]

If your at 25 mph , and it starts doing it , then you check the gears and it's in say 5th and you are at say 1300 rpms , then you pull it back in sport and nothing changes ? It should immediately rev up and downshift , tow will a little, sport alot...

Not trying to speak for the OP here, but mine is not so much RPM-related, but LOAD. He sees the trouble in gear and rolling, with a (very) light load (rolling resistance only, because slow speeds don't bring too much air resistance). Mine happens at light loads, AND at the lightest load of all, IDLE. AS soon as the load changes, the throttle opens to compensate, under ECM control. I can make mine MUCH worse by turning OFF the AC compressor at idle. I was leaning toward the PFI injectors being clogged because of the low speed, low load, but I read the thread referenced above re: the EGR DPFE Sensor / Valve. EGR is supposed to shut off at idle, but if there's a problem with the sensor or the valve, this may be just the ticket. Anyway, I'm going back to Ford with mine Real Soon Now. I've just put it off because they have failed twice now, and they "Have no Loaners available". I don't use my truck a lot, but when I need it, I NEED it, and can't be messing around for two weeks without it because it's sitting in the dealer's parking lot.

 

[NotBudule]

Mine is 100% low rpm in gear related , and it does kinda feel like rumble strips a little, but if I maintain it and hit tow , or sport it downsifts and is gone , the op said when he hits tow or sport , nothing changes gear wise , unless I misunderstood...if it's engine miss related , should be able to replicate that in the driveway with foot on brake and light accelerator to get some load on it... I would check that valve for water also ,or just replace it maybe...

 

[OrangeStreak]

Jim,
Have you checked the electronic outputs on your Damper? Improper settings have been known to release erratic signals that interfere with engine performance!

 

[FX4Offroad]

Jim,
Have you checked the electronic outputs on your Damper? Improper settings have been known to release erratic signals that interfere with engine performance!

Just checked it and THAT resolved it!!

I don't care WHAT they say about you Paul, you're OK in my book!

 

[FX4Offroad]

Hey Jim thanks! Hope you can convince Dave @AzScorpion of the same

I think we'll need $$.

Just sayin'

 

[OrangeStreak]

I think we'll need $$.

Just sayin'

 

[doug910]

Welcome to the club! I'm surprised no one has linked this thread yet. Several people have had the same issue, including myself.

https://www.ranger5g.com/forum/threads/bucking-surging-epidemic.14581/

It seems like replacing an EGR pressure sensor does the trick, but I fixed mine by replacing the spark plugs. Sucks that spark plugs lasted only $40k miles but it is what it is I suppose. Good luck!

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