Vacuum Leak? Rough idle

[FrankM5]

2019 GT, 41k miles Stock

Been noticing my car has been shaking on idle when I’m stopped at a light and watching the vacuum going from 21.4/20.4 to 19.6/18.4 it happens for a split second it’s starting to occur every day now at least once. Oddly enough it doesn’t ever happen in the morning only after work, it does have a Corsa intake no tune or anything.

any thoughts?

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[njweatherman]

Frank,

When it does this, what is your idle speed? On my 2020 GT automatic, I recently have noticed at a red light with my foot on the brake, that the idle will be steady around or just above 600, then suddenly drop down to 500, back to 600, etc. It will do this a few times and then stop. I'm waiting for it to either trigger a code, stall, or do it more frequently before making an appointment. From what I have read on the forum, it can be anything from a dirty throttle body, dirty mass air sensor, cam phasers, dirty vct solenoids, etc.

 

[Strokerswild]

My '19 F150 (5.0/A10) is going to the dealer tomorrow for this very thing. Fluctuating rough idle, stalling (one of which could have gotten me killed), and a couple of random CELs. I'm betting they will do a couple of reflashes per TSBs and send me on my way. Based on some things I'm seeing on the F150 forums this may or may not work, and if not it will go back in a multitude of times while they start throwing parts at it which will have mixed success. I love the truck, but all this has me planning to punt it before the warranty runs out in two years.

 

[njweatherman]

My '19 F150 (5.0/A10) is going to the dealer tomorrow for this very thing. Fluctuating rough idle, stalling (one of which could have gotten me killed), and a couple of random CELs. I'm betting they will do a couple of reflashes per TSBs and send me on my way. Based on some things I'm seeing on the F150 forums this may or may not work, and if not it will go back in a multitude of times while they start throwing parts at it which will have mixed success. I love the truck, but all this has me planning to punt it before the warranty runs out in two years.

Please keep us posted on what they end up doing. Thankfully, mine has not stalled yet.

 

[coz0502]

Frank,

When it does this, what is your idle speed? On my 2020 GT automatic, I recently have noticed at a red light with my foot on the brake, that the idle will be steady around or just above 600, then suddenly drop down to 500, back to 600, etc. It will do this a few times and then stop. I'm waiting for it to either trigger a code, stall, or do it more frequently before making an appointment. From what I have read on the forum, it can be anything from a dirty throttle body, dirty mass air sensor, cam phasers, dirty vct solenoids, etc.

This sounds very similar to what I was experiencing with my 16. I told my friend / neighbor who is a mechanic and he said clean the throttle body and MAF sensor. I tried it and there was quite a bit of residue on the throttle body, the MAF sensor was clean. It solved my issue. May want to give it a try, only takes 15 mins or so and cost nothing.

 

[Strokerswild]

Please keep us posted on what they end up doing. Thankfully, mine has not stalled yet.

FYI, the codes that resulted in my two CELs to date were P0021 (intake cam over advanced, bank 2) and P0301 (misfire in cylinder 1). The several instances that it has stalled haven't thrown a code. It's weird.

 

[DrZed]

... I had this rough idle happen once, vacuum seemed fine (PP1 gauges), but engine sounded like it was hissing and had a huge leak. Had a few codes (which I could remember), but they applied TSB 21-2174.

 

[Cobra Jet]

It sounds like this is a failing IMRC issue.

So if anyone has not had their upper intake replaced either by Warranty or other repair issues that requires the replacement of it - this thread outlines the actual reason the IMRC articulation fails and a DIY fix (that so far has worked).


This thread, another M6G member repaired the broken IMRC shaft using JB Weld and it was fully functional again after the repair.
https://www.mustang6g.com/forums/threads/our-first-dtc-p0308.160243/

99% of the time, the stumbling, rough idle or stalling can be attributed to complete IMRC failure or the IMRC is in the beginning stages of failing. The reason the IMRC fails is due to a broken actuator shaft. Looking at images of the shaft, the break is occurring because the diameter of the shaft is too small for the torque being applied by constant activation.
---

The other thing that causes rough idle concerns is the VCT system.

 

[Strokerswild]

Please keep us posted on what they end up doing. Thankfully, mine has not stalled yet.

Apparently my truck has a bad VCT solenoid, which will be replaced and I'll see where it goes.

If the F150 forums are to be believed, this may become a regular event.

 

[njweatherman]

Apparently my truck has a bad VCT solenoid, which will be replaced and I'll see where it goes.

If the F150 forums are to be believed, this may become a regular event.

Do you know how long a job like that takes?
Thanks for the update.

 

[Strokerswild]

Do you know how long a job like that takes?
Thanks for the update.

By the look of things, they're replaceable via two bolts once the valve cover is off, so it should be a fairly quick repair.

What I'm worried about is how long it will take to get the parts, since they won't let me have the truck back until it's been addressed.

 

[njweatherman]

By the look of things, they're replaceable via two bolts once the valve cover is off, so it should be a fairly quick repair.

What I'm worried about is how long it will take to get the parts, since they won't let me have the truck back until it's been addressed.

That stinks you cannot drive it. It's one of my big worries because my Mustang is my daily driver.

 

[Cobra Jet]

Apparently my truck has a bad VCT solenoid, which will be replaced and I'll see where it goes.

If the F150 forums are to be believed, this may become a regular event.

If VCTs had debris in them it surely will cause idle issues. There is a TSB or SSM that was issued a while back that mentions cycling the VCTs to try and push out any debris that may be causing the issue. If that does not work then obvious next step is replacements.

Supposedly the thought process is "debris" could be from dirty oil or something minute that was leftover from engine assembly gets into the VCT solenoid. Sometimes an oil change can "fix" the problem, as long as that problem was only related to minute debris in the VCT solenoid.

Here's (2) Threads for VCT info:
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/

 

[Strokerswild]

If VCTs had debris in them it surely will cause idle issues. There is a TSB or SSM that was issued a while back that mentions cycling the VCTs to try and push out any debris that may be causing the issue. If that does not work then obvious next step is replacements.

Supposedly the thought process is "debris" could be from dirty oil or something minute that was leftover from engine assembly gets into the VCT solenoid. Sometimes an oil change can "fix" the problem, as long as that problem was only related to minute debris in the VCT solenoid.

Here's (2) Threads for VCT info:
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/

The service department cycled the phasers in my truck and determined that there is a bad VCT solenoid, which is the first step with this driveability issue. I'm guessing it's been bad since the truck was new, as it's had the occasional odd miss since then which has progressed to the point of stalling and throwing CELs. I hope the parts get here ASAP, it solves the problem, and it's never an issue again.

 

[FrankM5]

Frank,

When it does this, what is your idle speed? On my 2020 GT automatic, I recently have noticed at a red light with my foot on the brake, that the idle will be steady around or just above 600, then suddenly drop down to 500, back to 600, etc. It will do this a few times and then stop. I'm waiting for it to either trigger a code, stall, or do it more frequently before making an appointment. From what I have read on the forum, it can be anything from a dirty throttle body, dirty mass air sensor, cam phasers, dirty vct solenoids, etc.

Hey thats exactly whats going on it stays at 600 then drops to 500 then shakes then goes back. Its starting to do it everyday for me at random times of the "drive"

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