RPM drops on 2019 GT

[Maclay74]

Mine didn't happen for like a month.
Your workaround is cool, but my car shaked for about 2-3 seconds, so maybe time of your reaction and AC kicking off is long enough so it stopped naturally?..

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[Cobra Jet]

If you're having idle issues there are many possibilities, but on this site it's been found to be 1 of 3 possibilities:

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

The VCT solenoids - operational issues can happen at any time with these, which will and does affect idle/drivability. Usually debris gets into the solenoid which could cause idle stumbles. Changing oil can flush out the debris or the Ford Service Center has a procedure that will flush out the VCTs without an oil change. I don't think a Service Center will do this voluntarily, only if a VCT code exists. I’m also not sure if there is a way to use Forscan to do a similar “flush” as a Tech @ Ford would using IDS.

Here's (2) 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/

2) IMRC function of intake. This seems to be more prevalent on the 2015-17, that's not to say it can't happen with the 2018+ too:
Check the IMRC articulation shaft. In 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 IMRC failures are due to the broken 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.

3) Other M6G members have found that idle or drivability issues were associated with the crank sensor (even if there are no codes OR there's a simple P0300). This could be your issue too, so review each thread carefully because each owner came across it in a different manner.

Check this thread:
https://www.mustang6g.com/forums/threads/misfire-at-high-rpm.174380/#post-3531453

AND this one:
https://www.mustang6g.com/forums/th...e-sensor-tone-ring.156234/page-2#post-3197692
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So yes, that's a lot of data coming back at you, but those are the most common sources of idle issues on the Coyotes.

 

[Gaz142]

Did you notice if it happen with AC on ? Mine seem to happen like yours but mostly with AC on. Also unsteady exhaust sound, like the sound of the exhaust goes quite then normal then quite etc prior to it happening. Car is with dealership for 1 week now.. they gonna replace all 4 vct.

 

[Gfswindle]

Started having the issue again Thursday evening with yesterday being very bad on my drive home. Checked codes with forscan and had P0011 pending, so I datalogged it happening in real time. Confirmed intake cam timing looking like a rollar coaster as the pcm tries to get them under control. I also logged solenoid duty cycle to see how much potential range of travel the valve in the phasers is actuated. Based on duty cycle alone at idle the change was only a few % meaning the range of motion needed to actuate the phaser is likely very very small meaning the window for error in manufacturing and tolerancing of the phasers is also incredibly small.

So I set out to figure out exactly what the failure mode may be on the phasers themselves. I remedied my problem temporarily with using the cycle the solenoids directly with 12v from a battery which got them back to working perfectly if only for a little while. Afterwards Idle was holding +- .5° so I proceeded to take manual control over the intake cams using forscan while logging the DC to see what drastically changing the desired angle would correspond to in the duty cycle itself. You can see that in the below picture. I'll explain; when you first start the vehicle intake cams are commanded +30 degrees which provides a smooth idle, after the warmup sequence has completed idle comes down and then +20 degrees is commanded. Knowing this I used forscan to drastically change the desired commanded angle and determined that when more power (duty cycle) is sent to the solenoid opening the valve which I presume reduces oil pressure to the advancement mechanism, this causes the cam angle to go negative.

Also you may notice just how stable my valve angle is after I used the cycle the solenoid method. It was rock steady for nearly 15 minutes of idle time. I cam back 30 minutes later and datalogged again and Bank 1 was rock steady while bank 2 was lazy and hunting its desired angle by about 3-4° suggesting that the phaser was sticking again.

So I say all that to make this conclusion. Something within the phasers is not allowing the solenoids to let oil escape properly or fast enough and/or the mechanism is binding causing the intake cams to reach their limit of travel internally from too much pressure which corresponds to -30 actual. By this time the PCM is trying to get ahold of the situation by reducing duty cycle and when they finally release, its like a flood gate opens dumping all their pressure bringing the cams to a more positive state than commanded which also sounded like a smoother and quieter exhaust tone in my observations. That explains when it happens how if the engine doesn't necessarily stumble but we hear the exhaust note changing sitting at a red light, it's because the angle hasn't gotten so bad negative as to cause idle problems but the intake cams are definitely hunting around while the PCM tries to bring them under control.

Either way, I now have to make a decision of do I want to tackle this repair myself, or find a shop to do it. I feel confident I could do it with the time and right tools but do I want to take a chance on messing something up.

 

[njweatherman]

Does anyone know if this low idle / stalling happens on all S550 Mustangs over-time or only on a select few?

 

[Gfswindle]

Does anyone know if this low idle / stalling happens on all S550 Mustangs over-time or only on a select few?

It really appears to random. This happened as far back as the gen 2 in 15-17 mustangs, f-150's with the coyote and if I'm not too mistaken, even 3.7l v6 models as they have appeared to use the same vvt phaser, could be wrong on that one though.

 

[ice445]

Started having the issue again Thursday evening with yesterday being very bad on my drive home. Checked codes with forscan and had P0011 pending, so I datalogged it happening in real time. Confirmed intake cam timing looking like a rollar coaster as the pcm tries to get them under control. I also logged solenoid duty cycle to see how much potential range of travel the valve in the phasers is actuated. Based on duty cycle alone at idle the change was only a few % meaning the range of motion needed to actuate the phaser is likely very very small meaning the window for error in manufacturing and tolerancing of the phasers is also incredibly small.

So I set out to figure out exactly what the failure mode may be on the phasers themselves. I remedied my problem temporarily with using the cycle the solenoids directly with 12v from a battery which got them back to working perfectly if only for a little while. Afterwards Idle was holding +- .5° so I proceeded to take manual control over the intake cams using forscan while logging the DC to see what drastically changing the desired angle would correspond to in the duty cycle itself. You can see that in the below picture. I'll explain; when you first start the vehicle intake cams are commanded +30 degrees which provides a smooth idle, after the warmup sequence has completed idle comes down and then +20 degrees is commanded. Knowing this I used forscan to drastically change the desired commanded angle and determined that when more power (duty cycle) is sent to the solenoid opening the valve which I presume reduces oil pressure to the advancement mechanism, this causes the cam angle to go negative.

Also you may notice just how stable my valve angle is after I used the cycle the solenoid method. It was rock steady for nearly 15 minutes of idle time. I cam back 30 minutes later and datalogged again and Bank 1 was rock steady while bank 2 was lazy and hunting its desired angle by about 3-4° suggesting that the phaser was sticking again.

So I say all that to make this conclusion. Something within the phasers is not allowing the solenoids to let oil escape properly or fast enough and/or the mechanism is binding causing the intake cams to reach their limit of travel internally from too much pressure which corresponds to -30 actual. By this time the PCM is trying to get ahold of the situation by reducing duty cycle and when they finally release, its like a flood gate opens dumping all their pressure bringing the cams to a more positive state than commanded which also sounded like a smoother and quieter exhaust tone in my observations. That explains when it happens how if the engine doesn't necessarily stumble but we hear the exhaust note changing sitting at a red light, it's because the angle hasn't gotten so bad negative as to cause idle problems but the intake cams are definitely hunting around while the PCM tries to bring them under control.

Either way, I now have to make a decision of do I want to tackle this repair myself, or find a shop to do it. I feel confident I could do it with the time and right tools but do I want to take a chance on messing something up.

You just did way more work than 90% of dealer techs would do trying to diagnose this issue. But it's nice proving that the intake phasers are the actual problem. However, one thing that's odd to me about the solenoid cycling trick is why it works at all, even for a limited time. I wonder if casting flash or some other junk is just getting perpetually stuck in the area? Would explain why some cars have this issue and some don't. My car has always had a steady hot idle, but every once in a while it seems "rough" even though I don't notice the tach moving.

 

[Gfswindle]

You just did way more work than 90% of dealer techs would do trying to diagnose this issue. But it's nice proving that the intake phasers are the actual problem. However, one thing that's odd to me about the solenoid cycling trick is why it works at all, even for a limited time. I wonder if casting flash or some other junk is just getting perpetually stuck in the area? Would explain why some cars have this issue and some don't. My car has always had a steady hot idle, but every once in a while it seems "rough" even though I don't notice the tach moving.

After some more research I discovered my assessment of how the phasers work was flawed as I assumed they operated solely on engine oil pressure alone. The following video proved otherwise and it's more complicated than that. They are a borg Warner design and they coined the term camshaft torque actuated phaser.



However the failure mode still stands, the spool valve as it appears is not allowing proper transfer of oil between the chambers as depicted. When dealing with very tight tolerance parts such as this it can be anything including varnish from oil and probably trash that can't find its way out. I believe cycling the solenoids, which moves the spool valves much further in their range of motion than any normal operation, causes unsticking from varnishes or dislodges any dirt that may have caused the spool valve to bind in any way.

It's my opinion however that the real problem is a tolerancing and/or surface finish problem which doesn't allow smooth operation. That is barring any real manufacturing defects such as burring on the valve or its mating bore.

 

[ice445]

After some more research I discovered my assessment of how the phasers work was flawed as I assumed they operated solely on engine oil pressure alone. The following video proved otherwise and it's more complicated than that. They are a borg Warner design and they coined the term camshaft torque actuated phaser.



However the failure mode still stands, the spool valve as it appears is not allowing proper transfer of oil between the chambers as depicted. When dealing with very tight tolerance parts such as this it can be anything including varnish from oil and probably trash that can't find its way out. I believe cycling the solenoids, which moves the spool valves much further in their range of motion than any normal operation, causes unsticking from varnishes or dislodges any dirt that may have caused the spool valve to bind in any way.

It's my opinion however that the real problem is a tolerancing and/or surface finish problem which doesn't allow smooth operation. That is barring any real manufacturing defects such as burring on the valve or its mating bore.

I wonder if some of the issue is poor clearancing/fitment allowing oil pressure inside the spool valve to bleed down enough at low RPM to where the PCM can no longer do fine adjustments? Especially given these cars run 5W20 with an oil pressure bypass for better efficiency, there probably isn't a lot to work with in the first place, let alone if there's junk clogging things or imperfect phasers. It would explain why there's a constant overshoot/undershoot on desired cam angle only in these conditions. If my suspicion is correct, I would suspect if you applied a load, like running A/C or even just holding the pedal down to bring it up to 3000RPM, that the advance angles logged would stop doing that nonsense.

I also can't help but wonder why Ford didn't put some sort of logic to detect when the PCM can't achieve its desired cam angle (or idle RPM for that matter) with a normal amount of adjustment given load conditions. Either that or they are very generous with allowed variance. I'm sure there's some valid engineering reason for why that may be, but I would still love to know.

I should log my car some time since it doesn't exhibit this problem. However, it does exhibit a "rougher" than usual idle every once in a great while. I put that in quotes because there's no misfire or RPM change that I can detect, but you can feel that each combustion event hits harder. The car almost has a slight cam lope. I'd love to know what profile is doing that or if it's the same problem, just not exhibited as severely as some of you guys.

 

[Gfswindle]

I first suspected oil pressure issues so I switched to 5w-30 and it didn't appear to have any effect, especially in my case as I have had it happen within the first 10 min of a cold start drive to a blazing hot day long drive. So I've almost ruled out oil viscosity.

Next time it happens I plan to log again and see how they act during a drive.

 

[Cobra Jet]

Can you elaborate as to the method used or how a M6Ger can manually "cycle" the VCT's? That's been a known issue per Ford SSM's and the method that Ford uses is utilizing IDS in order to clear the VCT's of debris. I don't think there has been any info to date or a DIY to do this outside of IDS like you did with a battery.

 

[ice445]

Can you elaborate as to the method used or how a M6Ger can manually "cycle" the VCT's? That's been a known issue per Ford SSM's and the method that Ford uses is utilizing IDS in order to clear the VCT's of debris. I don't think there has been any info to date or a DIY to do this outside of IDS like you did with a battery.

That's a good question, although I thought the official Ford method was exactly that, using a separate power supply to rapidly cycle them.

 

[Gfswindle]

Can you elaborate as to the method used or how a M6Ger can manually "cycle" the VCT's? That's been a known issue per Ford SSM's and the method that Ford uses is utilizing IDS in order to clear the VCT's of debris. I don't think there has been any info to date or a DIY to do this outside of IDS like you did with a battery.

That's a good question, although I thought the official Ford method was exactly that, using a separate power supply to rapidly cycle them.

Correct, I used a small agm battery from an old jump box with a pair of alligator jumper leads.

Pull the electrical plug from the vct solenoids, use the jumper leads and connect to the open terminals taking care not to create a short circuit by letting the leads touch. Take the small 12v battery, connect one lead to a battery terminal and then tap the other lead to the other repeatedly. I removed a solenoid and tested swapping polarities and observed that the solenoid functions the same no matter which terminal is positive or negative.

Forscan can be used to change the intake valve angle while the engine is running but this only creates a swing of a few percent duty cycle which doesn't amount to very much physical movement of the valve within the phaser.

 

[67go]

Thanks Cobra Jet and other members for your work on these problems. Just got the GT and will be on the lookout. Hopefully none!

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