Stumble / Occasional Stall at Idle

[Legion_s550]

Hello Everyone! Happy Friday!!


I've come across an issue with my Mustang (18 GT, PP1 10R80) where it stumbles, sputters, and sometimes stalls at idle. This issue is very noticeable on my Lund 93, FlexFuel, and E85R Tune. NO DTC's, NOT BAD GAS.

Car is mostly stock, just a drop in filter, and a Borla Cat back.

Lund told me after reviewing my logs that the cam is falling out of phase (likely a cam phaser issue, pretty common on fords), however, after i converted from my E85R tune (used the flex fuel to transition to 93, then once E85 is completely out of the tank, i flashed back to STOCK in preparation to bring the car to my dealer) and the stumble is MUCH better. Mind you, Brandon sent me the files, and all variants of my tunes from Lund have 0 revisions over what they sent me.

Previously, it would happen at almost every stop, whereas now, I can't seem to get it to do it on the stock tune.. While on the E85R tune, the pump gas tested at E83, and trims were very good. Between +2-4%.


As you can imagine, this puts me in quite a position. Do I take it to Ford with the Lund Tune in place (or leave it stock) or would you recommend Lund review my tunes?

Not sure why im so indecisive on this, but, was hoping to see if anyone can share their experience or knowledge on this.

Thanks for your time...

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[Basspro302]

Its not the tune, mine will do it randomly all the time then not do it for weeks. Usually more so when engine is hot.

 

[Legion_s550]

Its not the tune, mine will do it randomly all the time then not do it for weeks. Usually more so when engine is hot.

I didn't think it was necessarily. I was thinking that maybe it was exacerbating an underlying issue, but i'm not sure. I've driven it for about a week now with only 1 stumble. Previously, when I was on my tune, it would happen at nearly every stop. Probably just coincidence i guess...

 

[Basspro302]

Battery resets and changing oil for some reason seem to make it better. Im pretty sure its a phaser issue.

 

[Legion_s550]

Yep, new battery and oil and it still occured. You're right

 

[njweatherman]

I have this issue on my 2020 California Special. Like others have said, it mostly happens when the car is hot and stopped at a red light. Sometimes, it will happen a few days in a row, and then not show-up again for weeks. Luckily, mine has not stalled yet. When it happens on mine, the idle initially drops to 500 or so, and then fluctuates back and forth to 500 to 600, the car shakes, etc. One band-aid fix I have found that works on mine is when it begins to stumble, the car shakes and the idle drops to 500 or so, I immediately put the AC on and it raises the idle enough where the symptoms disappear. The dealer told me not to bring it in unless it stalls and/or I have CEL.

 

[Legion_s550]

I have this issue on my 2020 California Special. Like others have said, it mostly happens when the car is hot and stopped at a red light. Sometimes, it will happen a few days in a row, and then not show-up again for weeks. Luckily, mine has not stalled yet. When it happens on mine, the idle initially drops to 500 or so, and then fluctuates back and forth to 500 to 600, the car shakes, etc. One band-aid fix I have found that works on mine is when it begins to stumble, the car shakes and the idle drops to 500 or so, I immediately put the AC on and it raises the idle enough where the symptoms disappear. The dealer told me not to bring it in unless it stalls and/or I have CEL.

Good to know. Thanks for sharing that. Kinda sucks that your dealer wouldn't bother even looking at it without what you described...

In the event my dealer tells me the same, anyone have experience changing our the phasers and solenoids?

 

[njweatherman]

The problem with dealers today is that if the car does not show a code, they will not bother doing any further diagnostic testing.
From what I remember reading on here, changing out the VCT solenoids is an easier job than the cam phasers.

 

[Legion_s550]

Incase someone searches this - it ended up being the Cam Phaser Solenoid. Once i replaced those (I went ahead and just replaced them all with OE Replacements) the stumble is gone.

Thanks to those who provided input

 

[Cobra Jet]

Incase someone searches this - it ended up being the Cam Phaser Solenoid. Once i replaced those (I went ahead and just replaced them all with OE Replacements) the stumble is gone.

Thanks to those who provided input

Good to hear you got the issue resolved.

VCT's strike again.... LOL... there has to be a better aftermarket solution to the VCT's that exist as far as them being more robust or having a longer operational life span...

Just putting this below for future reference of this thread and VCT issues:

- VCT solenoids - if the solenoids are not operating properly due to debris or they are failing due to age, they can cause such issues as idle stumbles, stalling, and performance issues as well as a generic P0300.

This most recent thread, the culprit was the VCT solenoid::
https://www.mustang6g.com/forums/th...s-and-cam-retarded-codes.176734/#post-3571964

Here's (2) more threads for VCT info that I had previously posted in other threads:
https://www.mustang6g.com/forums/threads/2015-2021-s550-5-0’s-ssm-50067-vct’s-again-various-dtc-codes.169419/

https://www.mustang6g.com/forums/threads/p0018-code.123932/

 

[Legion_s550]

Good to hear you got the issue resolved.

VCT's strike again.... LOL... there has to be a better aftermarket solution to the VCT's that exist as far as them being more robust or having a longer operational life span...

Just putting this below for future reference of this thread and VCT issues:

- VCT solenoids - if the solenoids are not operating properly due to debris or they are failing due to age, they can cause such issues as idle stumbles, stalling, and performance issues as well as a generic P0300.

This most recent thread, the culprit was the VCT solenoid::
https://www.mustang6g.com/forums/th...s-and-cam-retarded-codes.176734/#post-3571964

Here's (2) more threads for VCT info that I had previously posted in other threads:
https://www.mustang6g.com/forums/threads/2015-2021-s550-5-0’s-ssm-50067-vct’s-again-various-dtc-codes.169419/

https://www.mustang6g.com/forums/threads/p0018-code.123932/

Thanks for taking the time to put this together. Loads of info in both of these threads

 

[MCS]

I just found this today thanks to @ice445

I had a supercharger installed and post-install the car stumbles and then stalls at stoplights. Below is an example of what it does sitting in my garage and not on the street. Yes, I had driven it back and was just backing it into the garage but figured it was safe to get a quick video here. Notice it is still in DRIVE. On the street it will do this and, more times than not, it will stall while I'm waiting at a stoplight with the car in D. It doesn't matter what mode (Normal, Sport, Track etc)




I'm going to point them in this direction. and see if maybe that's the golden ticket (no pun intended). Thanks very much for putting this info out there including your resolution sir!

 

[Temovic55]

Incase someone searches this - it ended up being the Cam Phaser Solenoid. Once i replaced those (I went ahead and just replaced them all with OE Replacements) the stumble is gone.

Thanks to those who provided input

Couldn't you have flushed them before replacing them >? wouldn't that help by any chance ?
Glad you figured it out eitherways!

 

[Legion_s550]

I just found this today thanks to @ice445

I had a supercharger installed and post-install the car stumbles and then stalls at stoplights. Below is an example of what it does sitting in my garage and not on the street. Yes, I had driven it back and was just backing it into the garage but figured it was safe to get a quick video here. Notice it is still in DRIVE. On the street it will do this and, more times than not, it will stall while I'm waiting at a stoplight with the car in D. It doesn't matter what mode (Normal, Sport, Track etc)




I'm going to point them in this direction. and see if maybe that's the golden ticket (no pun intended). Thanks very much for putting this info out there including your resolution sir!

You are very welcome! What you're explaining matches my experience as well. The solenoids we're getting stuck, causing -30 or more of timing , randomly at idle. I hope this fixes the issue for you as well. The parts themselves aren't that expensive.

 

[Legion_s550]

Couldn't you have flushed them before replacing them >? wouldn't that help by any chance ?
Glad you figured it out eitherways!

I'm not sure. However, the parts aren't that expensive, and if you have to take the solenoids out, mine as well replace it with a known good part. That way you don't have to take it apart again

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