FSDreamTeam forum
General Category => General Discussion => Topic started by: debbert on January 02, 2026, 03:41:02 am
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Since SU4, I, along with many other users are observing engine spiking issues around the Houston area. For me, this has occurred on the PMDG 737, 777, and the IFly 737 (at the very least). Prior to SU4, these issues didn't exist. This has been reported to PMDG by myself and a few others, HOWEVER, please read below regarding Coutal.
Additional users have reported that killing Coutal solves the issue. This is not a binding issue, community folder issue, etc. Those fixes have been attempted, and we have narrowed it down to what we think it is, something going on with Coutal. This issue is also ONLY happening below 18,000 feet, noticed shortly after departure up to 10,000 for the most part.
I want to reiterate that this engine spike issue is ONLY in the Houston area. For example, on climb out from IAH, or HOU (a video I will attach as a reply).
Here's an example I took, 777 departing out of IAH: This issue is duplicated at the very least, in the 737-800 and the IFly.
https://youtu.be/zd9tiHLoJz4. (https://youtu.be/zd9tiHLoJz4.)
Best,
Davis
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I'll add to this topic as we were doing a MSFS2024 group flight in and out of the Houston area today with the PMDG 737 and 777. Of those flying the 737, we encounter our throttle fluctuating and our autothrottles kept disconnecting and we couldn't get them to engage until we turned Couatl off. Then the engines operated normally and the plane flew fine. With the 777, taxing around the airport was fine but the moment we left the ground, the engines would surge and move all over the place. The plane throttles would move individually without input from users. We all had single axis configured for both engines. Once we turned Couatl off or got above 10,000 feet and away from the Houston area did the plane operate fine.
Yes I notified PMDG but I'm also posting here as turning off Couatl fixed the issue. Here is a video link of a user have the issue. During this flight we didn't discover that turning off Couatl fixed the issue. https://www.twitch.tv/videos/2658864169
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Here is the evidence on the newly released 737-800 as well. Notice how on this one, the Auto Throttle flicked off, and it's still spiking N1. On departure at Houston Hobby (HOU).
https://youtube.com/shorts/7OWMHbhuEYc?feature=share (https://youtube.com/shorts/7OWMHbhuEYc?feature=share)
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I was absolutely pulling my hair out the other night with this issue and experienced the same thing!! I'm glad I came across this thread because sure enough, I was in the area of HOU when it started happening. Was flying from BNA-SAT and over HOU my throttle kept disconnecting and engines were surging with the PMDG 737-800. Glad it's not just me!
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I was absolutely pulling my hair out the other night with this issue and experienced the same thing!! I'm glad I came across this thread because sure enough, I was in the area of HOU when it started happening. Was flying from BNA-SAT and over HOU my throttle kept disconnecting and engines were surging with the PMDG 737-800. Glad it's not just me!
I’m right there with you! It’s been very frustrating because you basically need to avoid the Houston area. I hope Umberto provides a fix soon. More and more people are reporting the issue in various communities. Reported to PMDG but after testing and other users we know it’s Coutal.
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I’ll add to this. I’ve been having this same issue in the iFly max8 as well as the PMDG 737-800 in the Houston area. I first experienced it with the max 8 on the SU4 beta, so I switched back to the main SU3 release at the time, and the issue went away. Then after the general SU4 release, the issue resumed.
I am not sure if relevant but I also could not load into the sim in the Houston area with Couatl running during the general SU2 and SU3 releases (specifically IAH). Now with SU4, I can load in to the Houston area with no issues except for this engine issue.
Link for the mentioned IAH/GSX issue: https://www.fsdreamteam.com/forum/index.php/topic,33602.0.html
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I'm also having this issue arriving and then departing from KIAH. Nothing more to add from what everyone says above.
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we couldn't get them to engage until we turned Couatl off. Then the engines operated normally
How do you "turn couatl off." I've restarted the couatl engine from the GSX menu multiple times and the engine surging continues. I cannot figure out how to "turn off" GSX.
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we couldn't get them to engage until we turned Couatl off. Then the engines operated normally
How do you "turn couatl off." I've restarted the couatl engine from the GSX menu multiple times and the engine surging continues. I cannot figure out how to "turn off" GSX.
From the windows taskbar in the bottom right you might have to click the little ^ to see it but there is a Couatl icon there. You can right click that and either exit or restart.
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Ahhh, thanks! Had no idea it was on the taskbar. I see it in task manager too. Looks like it can be started by running the .exe in the GSX program folder. I'll test this letter, but at least it seems like a workaround for flying into and out of the Houston area.
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Ahhh, thanks! Had no idea it was on the taskbar. I see it in task manager too. Looks like it can be started by running the .exe in the GSX program folder. I'll test this letter, but at least it seems like a workaround for flying into and out of the Houston area.
Yeah unfortunately some of us have been having to disable Couatl in the Houston area since SU2 for a couple of reasons. Hopefully there is information we can provide to Umberto to help troubleshoot further.
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This isn't really new news, but I just spent a good 60 minutes flying the 77L around KIAH with couatl.exe either running or not. Can confirm engine spikes occur with couatl.exe running and cease with it shutdown. Certainly odd, but it's consistent and repeatable.
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This isn't really new news, but I just spent a good 60 minutes flying the 77L around KIAH with couatl.exe either running or not. Can confirm engine spikes occur with couatl.exe running and cease with it shutdown. Certainly odd, but it's consistent and repeatable.
This is great news. I hope Umberto replies soon with a fix!
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Umberto,
Any updates regarding this widespread issue?
Thanks!
Davis
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More users over on the PMDG forum experiencing the issue. https://forum.pmdg.com/forum/microsoft-flight-simulator-2020-2024-products-discussion/pmdg-777/general-discussion-aa/377670-su-4-772-engine-power-spikes
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I just spent a good 60 minutes flying the 77L around KIAH with couatl.exe either running or not. Can confirm engine spikes occur with couatl.exe running and cease with it shutdown. Certainly odd, but it's consistent and repeatable.
I loaded the 77L at FSDT KIAH, and couldn't replicate it, see the video:
I read on PMDG forum, at least two users said it was fixed by clearing the airplane WASM cache, as suggested by PMDG. Now, you said you flew for 60 minutes, I only flew for 8 minutes around the airport so, does it mean I need to wait longer before the problem appears, or it should have already happened during that time ?
Note that, I had the Winwing software running, but I had all the various Winwing devices disconnected, so the software was likely not active. That's because someone suggested it might be related to it, but I still don't understand how it can also be related to KIAH.
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I’m not sure it’s specifically related to FSDT IAH. I think it’s just something about the Houston area. I flew into IAH last night from FLL and sure enough on final starting about 10 miles out and around 6000ft engine spikes started occurring killing the auto throttle in the PMDG 737. As soon as I killed Couatl, problem stopped. Restarted Couatl on the ground and all was good.
I followed the recommended WASM cache clearing from the PMDG forum and that didn’t resolve anything. Tried it it in both the PMDG 737 and the ifly max 8, both of which I’m seeing the problem.
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I’m not sure it’s specifically related to FSDT IAH. I think it’s just something about the Houston area.
That would remove an element of doubt then: I have FSDT KIAH installed and since I also saw users with this issue with and without it, I tested with, assuming it won't make any difference.
I flew into IAH last night from FLL and sure enough on final starting about 10 miles out and around 6000ft engine spikes started occurring killing the auto throttle in the PMDG 737. As soon as I killed Couatl, problem stopped. Restarted Couatl on the ground and all was good.
Do you have it if you start a flight at KIAH instead ?
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Yes I do also have it if I start at KIAH as well.
I’ll also add it’s not every flight. Some flights there are no issues, some flights the spiking is minimal, and others the spiking is so bad that over speed is inevitable. The only thing that changes that dynamically is weather. Not sure how weather + Couatl could impact engines but I’m trying to think of anything.
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Not sure how weather + Couatl could impact engines but I’m trying to think of anything.
That's what I don't understand either. As a general rule, GSX never change anything in the airplane status, it never writes to airplane variables (standard or custom), it only reads them.
The one and only notable exceptions are:
- during pushback, from the moment the crew says "bypass pin inserted" up until it says "bypass pin removed", the airplane position and heading is controlled by GSX, just position, heading and steering, nothing else.
- IF the airplane uses a standard fuel system (surely not PMDG then, since they are all flagged to use a custom fuel system), during the refueling, GSX will increase the fuel quantity. This basically happens only with default airplanes, and not even all of them.
Those are the only places where GSX ever writes something on the airplane. And of course, never in flight.
Fact I cannot reproduce it yet, seems to suggest there must be something else (another add-on) that it interacts with GSX, and that one is causing the engine spikes on the 777 or the A/T disconnect on the 737, so the effect stops when you close the Couatl engine because that addon might have realized GSX is not running anymore, so it stop whatever it was doing, so it would be useful to know which other add-ons you are running.
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Hi Umberto, I very much appreciate you taking the time to check this, and even posting the video of your test. I just deleted the WASM for the PMDG 777 and tried a flight departing KIAH (I do have FSDT KIAH installed). Unfortunately, the spiking commenced pretty much immediately. I tried switching weather to Clear Skies (not Live) and it made no difference. I also discovered that the spiking occurs even with A/T completely off (manual thrust). As per last time, I flew around KIAH at 4000 feet starting and stopping couatl64_MSFS2024.exe; spiking occurred only with couatl running as before.
For now, I have added a shortcut to Couatl64_boot.exe onto my desktop; whenever I fly into KIAH, and I will just kill couatl with task manager until I'm on the ground, and then run Couatl64_boot.exe before taxiing to my gate.
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Hi Umberto. Here is my full list of addons with the exception of airports used via addon linker.
here is my list:
Aerosoft CRJ
Dirty 30 and Liveries
Elevatex Bridge
Fenix 319,320,321 and Liveries
FSLTL Traffic Base
FSUIPC 7 WASM Event Module
ifly 737 Max 8 and Liveries
IVAO_MIL
Miltech MH60
Mobiflight Event Module
Navigraph EFB Charts App
Navigraph EFT Simbrief App
Navigraph NAV Base
Navigraph Nav Jepp
P42 Chaseplane
PMDG 738 and Liveries
PMDG 777 and Liveries
Winwing WWTWSAM
Boris 737 Audio
Boris 777 Audio
Boris CRJ Audio
GSX Pro
GSX World
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Hi Umberto. So another update. Myself and szln6z connected on discord and actually compared our list of addons. Szln6z went through the efforts of testing each addon one at a time we both found the same results below. I will let szln6z speak for themselves but in my case, we narrowed it down to FSLTL and GSX. When Coualt and FSLTL are installed/running at the same time, we get the engine spike issue. As you know when we disable Couatl via task manager, the issue goes away. The new part is when we uninstall or remove FSLTL from the community folder, the issue also goes away, even if we keep Couatl running.
So in short:
GSX alone in IAH area = no issues.
FSLTL alone in IAH area = no issues.
GSX + FSLTL in IAH area = engine spiking issue.
***Update after posting this information in FSLTL discord***
From BirdmanRS: So somehow the AI models/animations/soundpacks in FSLTL Base Models, injected by some other tool, are modifying the user controlled aircraft? Interesting.
My response: That’s what seems to be the case. The strangest part is it’s only in the area of KIAH that we have found so far (both default and 3rd party scenery) and only when GSX (Couatl) is running at the same time, and only for some users. I did add these test results over on the FSDreamTeam forum post we have going so hopefully Umberto will have some ideas as well.
From BirdmanRS:I can confirm there is absolutely nothing in Base Models that is location specific.
If you find out more, let us know.
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I tried with FSLTL as well, had one UAL model placed in the hangar, and couldn't see any spikes so, maybe, it's not "just" having FSLTL installed, but might depend on which model, since the one selected is chosen at random amongst all the available ones in the UAL livery.
I might try making a change to the KIAH code to spawn the model with its simulation completely disabled, I'll let you test a changed file soon.