Bucking/Surging Epidemic

airline tech

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Yeah, still having the feeling of hesitation occasionally when driving with very light throttle at constant speed around town. I know the main recommendation is to replace the pressure sensor, but has anyone replaced the valve or actuator that complements the sensor? (In case it’s the same effect but different part to blame?)
Light throttle & constant speed = (?) MPH
Does it have the same feeling if in Sport Mode?

I am thinking you are feeling the transmission skip 2nd gear, feels like you are on a slightly bumpy road, give it more throttle and it smooths out.
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Msfitoy

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Prior to sensor fix, I described the sensation while trying to maintain 25mph (with or without cruise control) the throttle felt like it was rocking on/off on/off creating a light but annoying jerking motion...no gear change involved...
 

notsolinear

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Light throttle & constant speed = (?) MPH
Does it have the same feeling if in Sport Mode?

I am thinking you are feeling the transmission skip 2nd gear, feels like you are on a slightly bumpy road, give it more throttle and it sooths out.
The issue I’m feeling is happening around 30 or 40mph, steady speed, often in 7th gear. Flat ground and I can watch the gear indicator it’s not changing. I also feel the sensation every few seconds and it’ll happen for an extended period of time.
 

Msfitoy

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The issue I’m feeling is happening around 30 or 40mph, steady speed, often in 7th gear. Flat ground and I can watch the gear indicator it’s not changing. I also feel the sensation every few seconds and it’ll happen for an extended period of time.
Your DPFE sensor is not fixed...
 

notsolinear

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Your DPFE sensor is not fixed...
Any suggestions for how to proceed? Bought the assembly with hoses from Levittown, installation went smoothly. Anyone else had one dead-on-arrival? Is there anything I can check to diagnose it as faulty to rule out some other issue?
 


airline tech

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There are quite a few variables and sensor inputs that tie into the EGR system, since my last try at looking for PIDs for the DPFE, Autel has released Ford updated data, so I have now expanded troubleshooting data available than the previous software level.
I can see if I can pull up normal data related to the EGR system.

Are you able to pull any codes in history and were codes (if any) cleared after you replaced the DPFE sensor?
Most likely code P139C

Is the coolant level full and maintain full?
Are you having to add small amounts of coolant periodically?

As far as the DPFE sensor, there is a test of the sensor, tests the sensor reading and reaction time with vacuum gauge while monitoring the voltage change on the Scan Tool (PID) or with a multimeter (back probing) the connector.
Posted somewhere above as well as a fairly detailed system operation.
 

landiscarrier

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Ok, fine! I replaced mine too! Not really sure if I have a surging or bucking issue but at just about 80k maybe I'm just use to it! haha! Anyway, replaced this AM and I have a lot of driving to do today so I'll see if I notice any difference.
 

airline tech

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Not quite the Data Pids I wanted to show, but at least with a capable scan tool you can see the system and get it to activate without a Vacuum Pump.

Now to clarify scan tools will sometimes display opposite of what you want to view.
With my Autel the DPFE is displayed in PSI vs Voltage

So, we take the test procedure for the DPFE, note these parameters have been updated to a more accurate reading in the current manuals.

Normal: (KOEO) = Key On Engine Off
1.3 to 1.7 Volts or (-0.06 PSI) - which should show a average reading of 1.5 Volts. (No-Flow)

Now when you start the engine and are at idle, this reading should not change.
Reason the EGR Valve is closed (No Flow)

The manual has you disconnect the hoses at the DPFE and apply a vacuum to the sensor and record your voltage readings / PSI.

Apply a vacuum of 8-9 Inches of vacuum to the small port of the sensor and hold for 10 seconds.
you should see these PID readings on the DPFE Sensor

2.5 Volts or 3.62 PSI (25 KPA - Converted)

Release the vacuum and the sensor reading should return to original reading within 5-Seconds.

Now to understand (1) factor for the EGR system to operate, the engine has to be under a load.

So, a quick alternate way to see the EGR Valve open and close without a full-on test is this:

Bring engine to operating temp and hook up scan tool and bring up relevant PIDs.

Take at IDLE readings of the DPFE sensor with the EGR Valve closed, should be closed at IDLE

Set the parking brake and place into drive:

HOLD BRAKE PEDAL

Increase RPM to about 2,000 RPM
You can now see the EGR Valve open (to about 10%)

Now you look at the DPFE sensor PID, the Voltage & PSI should rise, indicating FLOW, a second verification of flow is the MAP Sensor (PSI) Rise, exhaust flow into the Intake.

A third verification of flow is the Exhaust Press Sensor voltage rise:
Note this is not the DPFE sensor, this is the Exhaust Back Pressure sensor downstream of the EGR Cooler. The system uses this input as a source of data for actual EGR Valve position.

Bring engine back to idle, and all of the IDLE PID readings should return within 5-Seconds.

Basically, a simple test, to ensure that the EGR Valve opens and closes and also checks at least partially the DPFE sensor's ability to sense flow and return to no flow readings.

What you are looking for: DPFE Readings, you want to ensure that the DPFE sensor is reading (zero flow) when the EGR valve is closed, and you want it to sense flow when the EGR valve opens

This is not a full-on test of the system but at least gives the ability to get the DPFE sensor to activate.

Being that (IF CODED) the most common code reported is P139C, this code is generated by the EGR system monitor (Test Results)

Once per drive cycle, the system will perform self-tests, normally at Idle but due to the ASS system this is performed OFF Idle.

Part of this test is closing the EGR Valve and looking at the DPFE sensor readings.
If the sensor is out of range (Lower or Higher) than normal it will trigger code P139C
Now a Bad Sensor, Plugged Orifice Tube or Disconnected or Lose Hose can be at fault.

A faulty DPFE sensor is the most common, so it is not reading flow when the EGR valve opens, or it is reading flow with the EGR valve closed. (Lower or Higher) than normal readings or inaccurate flow readings when the EGR Valve opens, reading higher or lower flow rates compared to actual valve position.
This flow rate along with the EBP (Exhaust Backpressure) reading, determines the EGR valve open position with various other data inputs.

Example PID's at Idle:

EGR Valve Closed.jpg



ERG Valve Open @ 2000 RPM

EGR Valve Open.jpg



This test will be helpful, for those low speed (Low RPM) stumbles, hesitation issues.
as you can see the EGR Valve Open and Close.
If you feel the stumble, hesitation or bucking while doing this test, look at the DPFE sensor readings and EGR Valve position or do an Indepth troubleshooting test.
 

GBryant155

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I changed the dpfe sensor on my ranger Friday evening. All I can say it’s like driving a different truck. 25-40 mph smooth as glass and seems smoother cruising at 60-65 mph
 

notsolinear

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Are you able to pull any codes in history and were codes (if any) cleared after you replaced the DPFE sensor?
Most likely code P139C

Is the coolant level full and maintain full?
Are you having to add small amounts of coolant periodically?

As far as the DPFE sensor, there is a test of the sensor, tests the sensor reading and reaction time with vacuum gauge while monitoring the voltage change on the Scan Tool (PID) or with a multimeter (back probing) the connector.
Posted somewhere above as well as a fairly detailed system operation.
@airline tech I appreciate this info and all the other info you've shared. I haven't had any trouble codes before or after I first noticed the behavior last November. Coolant level full, haven't had any change in that since I bought used a year ago. I don't have a vacuum tester (ordered a cheap one today), but I hooked up the original DPFE sensor to 5V at my bench today and measured the output while I used my lungs to change the pressure on either tube: Saw it resting at ~1.46V increasing or decreasing by more than a volt depending on what I was doing. Not sure what that tells me except that it's not catastrophically broken?

I don't currently have a scan tool that'll let me view those other PIDs although I did pull out the one I have tonight on a 2 mile drive and noticed that the misfire counts were 1, 0, 2, and 5 for Cylinders 1-4 (current driving cycle). Never looked at those numbers before, but seems high for such a short period of time?

Even though it seems exceedingly unlikely that the new DPFE sensor I ordered is also bad, part of me wonders if another $80+shipping on a second replacement is still cheaper than taking it to the dealer to investigate (outside of 36k warranty). If the second replacement still doesn't fix it, then I can give in to paying the dealer to diagnose.
 

notsolinear

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Pressure tester tool showed up in the mail today so I hooked up to my original (now replaced) DPFE sensor, powered by 5.0v at the bench. With 9 inHg vacuum on the shorter tube it reads 3.28v, with 9 inHg vacuum on the longer tube it reads 0.29v. When I bleed the vacuum it updates to 1.43v in a split-second. I tried leaving the vacuum on either port for 30+ seconds and there was no observable leak. I guess the next thing to check would be what the truck reads (in case there's an issue in the connector or harness?)
 

Yinzcity

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Had a chance to do some testing today with some of the old sensors I have replaced on my truck. I've changed about 5 out in the 42k I've had it chasing a studder/missfire at tip in. The sensor replacement does seem to make a difference for a bit, but it always ends up deteriorating. Some days worse than others, it does better in the winter and when it's dry and worse on cool damp days.

I tested 3 sensors I had replaced on the truck because of hesitation before. I tested on the bench with a 5V power supply and a handheld vacuum pump. I'm comparing function against the specs Airline Tech posted above

At atmospheric, all 3 sensors read 1.5V, so that checks out ok.
1000002789.jpg


At 8in vacuum, I'm reading 2.7V. I'm guessing that's close enough to 2.5 and that my vacuum gauge isn't that precise.
1000002790.jpg


All 3 sensors returned to 1.5V as soon as I dropped vacuum to atmospheric, so I can't see anything wrong there even though they weren't working well in the truck.

I also opened up one to take a look inside. There's not much there, just a single sensor that sees pressure from each port on each side, hence the differential in differential pressure sensor. I did notice that the sensor face is potted with some kind of material. This should mean that the water we see in the sensor when it's removed shouldn't affect it.

1000002794.jpg

1000002795.jpg


1000002797.jpg
1000002798.jpg
1000002799.jpg


So I'm stumped. Not sure what actually breaks in the sensor or maybe it's a temporary condition and it goes away when the sensor sits. I suppose I could pull the sensor that is currently on my truck and test it. It's not the worst it's been, but it does.have hesitation occasionally...
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