2017 Ford F250 6.7 PowerStroke

Adam Technician Midland, Texas Posted   Latest   Edited  
Question
Driveability
2017 Ford F-250 Super Duty Platinum 6.7L (T) 6-spd (6R100)
Turbo Flutter
Engine Surge

Hello to all first time posting here so here goes nothing. I have a 2017 F250 6.7 Power Stroke. Customer concern is at highway speeds light throttle boost gauge on cluster fluctuate 0-10 psi and engine will surge. Test drove vehicle and verified that it indeed does surge and boost gauge fluctuate but only when truck is in regen.I pid monitored some pids and upload a screen shot of what found. The picture i upload are readings taken at idle. i seen this before and ford has tsb but for older model 11-16 model years to replace exhaust valve as they claim that they are sticking. This tsb of course does not apply for this year but its exactly what's wrong so i will be replacing all 16 exhaust valves. So my question is how does sticking exhaust valve affect my Maf and Map readings causing them to fluctuate as seen in this picture which i took when it was idling? Im curious because im taking the CTI online class pressure waveform analysis and trying to picture in my mind if i could see this in psi sensor scope what it would look like and how is it that my exhaust valves affecting intake psi ?

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Chris Technical Support Specialist
Commack, New York
Chris Default
 

The TSB states to update the PCM and if the concern was present during regen to replace only the Left Bank exhaust valves. It is an odd TSB but I would suspect it has something to do with temperature issues in the left head during regen. The build dates effected are built on or before 23-Feb-2016. I would check the engine tag for build date as it may have been built before the vehicle. I…

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Adam Technician
Midland, Texas
Adam Default
 

This truck has latest calibration using ids 118.03. Ford engineering has got back to me saying replace all 16 exhaust valve since updated pcm tune fires both banks during regen. I went ahead and test drove like truck and did does not act same way. Unfortunately they couldn't answer my question as to how the valves are affecting my intake psi. He was able to tell me that the turbo flutter due to…

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Tyler Owner/Technician
Fort St. John, British Columbia
Tyler Default
 

Did you monitor the vgt position actual and desired by anychance?

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Adam Technician
Midland, Texas
Adam Default
 

Yes they both are matching and follow each other.

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Chad Technician
Decatur, Alabama
Chad Default
 

You need to monitor EGR valve command and actual position while concern is present. I’ve had a couple of EGR valves sticking open when commanded closed. This causes a drop in EBP and Map and will start to surge. I’ve done the exhaust valve TSB on the older models with mixed results.

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Kevin Owner/Technician
Litchfield Park, Arizona
Kevin Default
 

That would also explain the low MAF. RPM seems a bit low at 536.

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Chad Technician
Decatur, Alabama
Chad Default
 

Yea I really wanna see EGR and EBP pids while this is happening. Also he’s a little higher in elevation than me, but I feel like his Baro is low too along with the RPM.

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Adam Technician
Midland, Texas
Adam Default
 

I did monitor my EGR command and actual both stayed at 4.5% closed. Watched my EGRTC pid as well an temp never rose so I knew egr wasn't leaking. I replaced all 16 valves and fixed my concern. Thanks for response

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Chad Technician
Decatur, Alabama
Chad Default
 

It would have been interesting to look at power balance and do a relative compression test while the concern was present to see if you could pinpoint it to any one cylinder. Did the truck have a lot of idle hours?

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Marlin Technician
Estacada, Oregon
Marlin Default
 

When an exhaust valve remains partially open during an intake stroke, part of the cylinder fill comes from the exhaust. This reduces VE and lessens the pressure drop in the intake. This is exacerbated by increased exhaust back pressure, as is caused by a turbocharger. The valve probably closes when the piston moves upward.

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Adam Technician
Midland, Texas
Adam Default
 

Marlin thanks this now makes sense to me. This is what I was looking for now I can picture it in my head and see what happening.

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Adam Technician
Midland, Texas
Adam Resolution
 

Thanks everyone for replies my question was answered. Also I went ahead and replaced all 16 exhaust valves and concern is fixed.

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Marlin Technician
Estacada, Oregon
Marlin Default
 

Is there any visible sign of the problem or of the results?

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