2021 Fuel Pressure Fluctuations and Roughish idle

[Whiplash25]

Hey all, This might be my first post on here and it’s gonna be a long one.
Anywho, I am working thru an issue with fuel pressure fluctuations at idle and under load. The truck is a 21 6.7 SO with the 68RFE, Ez Lynk with CCS tuning, Black Market Performance Cat filters front and rear, and a Banks CAI, with 24k miles, no warranty.

So I noticed the issue about a week ago after exiting the freeway and sitting at a red light. Truck was acting almost like it had a random misfire. I checked codes and got U0002 which came back as pretty much nothing. Deleted code and it never came back. No CEL no issues until this past weekend. The wife and I we’re coming back from the store and came to a stop sign. Same issue of a rough idle, no code this time. Got home stopped in the driveway, same issue. Moved the shifter to park, issue stopped intermittently, then started the rough idle but at a slower interval. Moved the shifter to reverse, same issue, faster interval. Moved shifter to drive, same interval as reverse.

Researching on it from past generations of 6.7’s has lead me to FCA, Fuel Filters, MAP, IAT, and finally HPFP and injectors. Just trying to rule out the common denominator I have re-flashed the truck to a refreshed version of the current tune, and verified there is no water in fuel.

Drove across town to an appointment and noticed when I would roll off the throttle and back onto it I could watch the fuel injection pressure drop to 2.5k psi and the rebound to between 6 and 8 k psi. Rough idle was back, not as noticeable but still there. After I got home I reflashed to stock fuel mapping to verify issue is not being caused by software and is coming from a hard part. Which is where I am now.

Current plan of attack is to swap back to OEM filters as I cannot confirm flow ratings of CAT filters. Run Hotshots Diesel Extreme thru fuel system, I already run Hotshot EDT on every fill up. Verify no possible leaks or air suction at any of the low pressure fuel system. Check volume and pressure of lift pump. After that I am down to replacing parts. All sensors minus FCA have been checked and cleaned.

Any ideas from the folks on here? Dealership is not an option.


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[GPurcell01]

Been there done that and I'm going to save you a lot of time and frustration.

It's the tuning which is unfortunate because I liked it.

Went through 35+ revisions and they could never get it figured out. Switched to a different tuner and life is good.

The interval you're feeling is the load change of the A/C compressor kicking on and off at idle and it initiates the fuel hiccup.

 

[Whiplash25]

I forgot to add. Ac was off. 75 degrees and the winders are down.


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[H3LZSN1P3R]

Been there done that and I'm going to save you a lot of time and frustration.

It's the tuning which is unfortunate because I liked it.

Went through 35+ revisions and they could never get it figured out. Switched to a different tuner and life is good.

The interval you're feeling is the load change of the A/C compressor kicking on and off at idle and it initiates the fuel hiccup.

You are the first i have heard that has had those issues with CCS, they are one of the better tuners out there in my experience almost everyone around here runs their tunes, who did you go with?

 

[GPurcell01]

You are the first i have heard that has had those issues with CCS, they are one of the better tuners out there in my experience almost everyone around here runs their tunes, who did you go with?

Had this issue with my HO although it manifested slightly different and my father's SO was exactly as described. In CCS's defense the tuning was good otherwise and the support was top notch.

 

[H3LZSN1P3R]

Had this issue with my HO although it manifested slightly different and my father's SO was exactly as described. In CCS's defense the tuning was good otherwise and the support was top notch.

I had one little issue with mine but its the CP4 causing the problem the guys were great and even worked with me and we changed up the tune parameters to work with my CP4.

 

[Whiplash25]

I called CCS and got a new 21 friendlier tune that seems to be working better. It’s not dropping rail pressure on accel or decel and the stumble at idle is gone. There is still a bump in the truck when at a stop and in drive, but that could be trans unlocking and still learning. I will update again once I have put several hundred miles on this tune. Thank god it wasn’t hard parts.

Edit: CCS did say if you have a 21 truck the tuning for those is a different animal when compared to the 19-20 trucks. Must be the magic smoke and machine learning in the ecm.

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[H3LZSN1P3R]

I called CCS and got a new 21 friendlier tune that seems to be working better. It’s not dropping rail pressure on accel or decel and the stumble at idle is gone. There is still a bump in the truck when at a stop and in drive, but that could be trans unlocking and still learning. I will update again once I have put several hundred miles on this tune. Thank god it wasn’t hard parts.

Edit: CCS did say if you have a 21 truck the tuning for those is a different animal when compared to the 19-20 trucks. Must be the magic smoke and machine learning in the ecm.

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Is thats why i got a bunch of new IA25 tunes pushed to my EZ-Lynk app this evening? Lol

 

[GPurcell01]

I called CCS and got a new 21 friendlier tune that seems to be working better. It’s not dropping rail pressure on accel or decel and the stumble at idle is gone. There is still a bump in the truck when at a stop and in drive, but that could be trans unlocking and still learning. I will update again once I have put several hundred miles on this tune. Thank god it wasn’t hard parts.

Edit: CCS did say if you have a 21 truck the tuning for those is a different animal when compared to the 19-20 trucks. Must be the magic smoke and machine learning in the ecm.

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This is good to know - I hoped he was able to get it figured out. Both of ours are '21 so makes sense. Back in Jan/Feb he did not have it.

 

[Whiplash25]

Is thats why i got a bunch of new IA25 tunes pushed to my EZ-Lynk app this evening? Lol

You’re welcome? That is exactly what they said to run. He said their 21 test truck only has like 400 miles on it and they don’t spend a lot of time on it specifically as there are more 19’s and 20’s needing tunes and revisions.


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