What is the current state of the 'engine stumble' issue?
02-12-2024 | 12:42 AM
#617
Intermediate
Joined: Feb 2020
Posts: 45
Likes: 1
From: Southern MA
This exact thing happens to me in my 991.2 gt3 and it's been almost 2 years since I've had the car. It's an annoying quirk I've found that I'm finally trying to figure out.
Did anyone on here find out why our cars do this?
Sorry to revive old posts. I replaced throttle body, map, air filters, plugs, did smoke test for vacuum leak...no change when letting off throttle abruptly as it does the small flutter. also idle has very small fluctuation maybe 25-50 rpm. not sure If that's normal but no other car I've had did that. otherwise drives great.
Did anyone on here find out why our cars do this?
Sorry to revive old posts. I replaced throttle body, map, air filters, plugs, did smoke test for vacuum leak...no change when letting off throttle abruptly as it does the small flutter. also idle has very small fluctuation maybe 25-50 rpm. not sure If that's normal but no other car I've had did that. otherwise drives great.
Last edited by jtdr35gtr; 02-12-2024 at 12:45 AM. Reason: clarity
02-12-2024 | 04:45 PM
#618
Instructor
Joined: Mar 2022
Posts: 158
Likes: 78
From: Miami
This exact thing happens to me in my 991.2 gt3 and it's been almost 2 years since I've had the car. It's an annoying quirk I've found that I'm finally trying to figure out.
Did anyone on here find out why our cars do this?
Sorry to revive old posts. I replaced throttle body, map, air filters, plugs, did smoke test for vacuum leak...no change when letting off throttle abruptly as it does the small flutter. also idle has very small fluctuation maybe 25-50 rpm. not sure If that's normal but no other car I've had did that. otherwise drives great.
Did anyone on here find out why our cars do this?
Sorry to revive old posts. I replaced throttle body, map, air filters, plugs, did smoke test for vacuum leak...no change when letting off throttle abruptly as it does the small flutter. also idle has very small fluctuation maybe 25-50 rpm. not sure If that's normal but no other car I've had did that. otherwise drives great.
02-12-2024 | 05:01 PM
#619
Pro
Joined: Feb 2018
Posts: 737
Likes: 305
From: Texas
if you have a dramatic drop or fluctuations in RPM, sure the throttle body or VVT solenoids might need to be replaced.
but 25-50 rpm fluctuations is "normal".
as for the stumble.
two variations of it.
one is a dead stop stumble. no one knows the cause.
other is a little tug/hesitation/stutter... when car is climbing slowly through the 2 to 3K rpm range.
mine has DRMATICALLY improved after i replaced my engine oil cap.
I am wondering if the PCV valve/solenoid might need to be replaced. this thing:
https://dvizok.com.ua/ru/product/13969354193/
https://www.fcpeuro.com/products/porsche-vapor-canister-purge-solenoid-boxster-cayman-por-9a111009321
but 25-50 rpm fluctuations is "normal".
as for the stumble.
two variations of it.
one is a dead stop stumble. no one knows the cause.
other is a little tug/hesitation/stutter... when car is climbing slowly through the 2 to 3K rpm range.
mine has DRMATICALLY improved after i replaced my engine oil cap.
I am wondering if the PCV valve/solenoid might need to be replaced. this thing:
https://dvizok.com.ua/ru/product/13969354193/
https://www.fcpeuro.com/products/porsche-vapor-canister-purge-solenoid-boxster-cayman-por-9a111009321
Last edited by Sajan; 02-12-2024 at 05:02 PM.
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subshooter (02-12-2024)
02-12-2024 | 08:36 PM
#620
Intermediate
Joined: Feb 2020
Posts: 45
Likes: 1
From: Southern MA
@Sajan That is interesting that the oil cap helped the stutter climbing 2-3k rpm. I wonder if that is related to pressure loss. I'll be trying this. At this point anything not very expensive I'll try.
Sometimes it's like my car doesn't know if I want gas or no gas as well. It sort of bounces slightly when I'm between throttle/ no throttle. I had a 997 turbo and it exhibited none of my issues described here, although these might be better classified as quirks.
I've tried replacing the throttle body (no change in idle stumble) but as suggested by @dannyk304 I think the cam solenoids might be next on my agenda. I've done everything else as mentioned above (plugs, vacuum test, tb, filters). Car does drive great aside from the idle and strange but small rpm flutter when letting off. I saw a few others posting about the same flutter on a gt3rs so not sure if this is just part of owning a high performance Porsche as opposed to other brands.
Again, my old 997 didn't exhibit any of these symptoms though. Do all 911's not filter out idle fluctuations?
I really appreciate the quick and friendly responses from everyone on here. I usually just read posts and rarely post myself. This is very helpful.
Sometimes it's like my car doesn't know if I want gas or no gas as well. It sort of bounces slightly when I'm between throttle/ no throttle. I had a 997 turbo and it exhibited none of my issues described here, although these might be better classified as quirks.
I've tried replacing the throttle body (no change in idle stumble) but as suggested by @dannyk304 I think the cam solenoids might be next on my agenda. I've done everything else as mentioned above (plugs, vacuum test, tb, filters). Car does drive great aside from the idle and strange but small rpm flutter when letting off. I saw a few others posting about the same flutter on a gt3rs so not sure if this is just part of owning a high performance Porsche as opposed to other brands.
Again, my old 997 didn't exhibit any of these symptoms though. Do all 911's not filter out idle fluctuations?
I really appreciate the quick and friendly responses from everyone on here. I usually just read posts and rarely post myself. This is very helpful.
02-13-2024 | 10:06 AM
#621
Pro
Joined: Feb 2018
Posts: 737
Likes: 305
From: Texas
@Sajan That is interesting that the oil cap helped the stutter climbing 2-3k rpm. I wonder if that is related to pressure loss. I'll be trying this. At this point anything not very expensive I'll try.
Sometimes it's like my car doesn't know if I want gas or no gas as well. It sort of bounces slightly when I'm between throttle/ no throttle. I had a 997 turbo and it exhibited none of my issues described here, although these might be better classified as quirks.
I've tried replacing the throttle body (no change in idle stumble) but as suggested by @dannyk304 I think the cam solenoids might be next on my agenda. I've done everything else as mentioned above (plugs, vacuum test, tb, filters). Car does drive great aside from the idle and strange but small rpm flutter when letting off. I saw a few others posting about the same flutter on a gt3rs so not sure if this is just part of owning a high performance Porsche as opposed to other brands.
Again, my old 997 didn't exhibit any of these symptoms though. Do all 911's not filter out idle fluctuations?
I really appreciate the quick and friendly responses from everyone on here. I usually just read posts and rarely post myself. This is very helpful.
Sometimes it's like my car doesn't know if I want gas or no gas as well. It sort of bounces slightly when I'm between throttle/ no throttle. I had a 997 turbo and it exhibited none of my issues described here, although these might be better classified as quirks.
I've tried replacing the throttle body (no change in idle stumble) but as suggested by @dannyk304 I think the cam solenoids might be next on my agenda. I've done everything else as mentioned above (plugs, vacuum test, tb, filters). Car does drive great aside from the idle and strange but small rpm flutter when letting off. I saw a few others posting about the same flutter on a gt3rs so not sure if this is just part of owning a high performance Porsche as opposed to other brands.
Again, my old 997 didn't exhibit any of these symptoms though. Do all 911's not filter out idle fluctuations?
I really appreciate the quick and friendly responses from everyone on here. I usually just read posts and rarely post myself. This is very helpful.
yours might be a whole different issue than the infamous stumble this thread is about..
02-13-2024 | 01:47 PM
#622
Intermediate
Joined: Feb 2020
Posts: 45
Likes: 1
From: Southern MA
here is a link to my car's idle (991.2) gt3. Just seems to fluctuate way more than would seem acceptable:
As @sampelligrino mentioned in post 397 of this thread my car also does the exact thing described when lifting off throttle, like there is a slight flutter/stumble when coming off throttle too quickly. Very similar to 2:04 in this video, see tach in video (no affiliation): flutter_liftingoffthrottleyoutube
As @sampelligrino mentioned in post 397 of this thread my car also does the exact thing described when lifting off throttle, like there is a slight flutter/stumble when coming off throttle too quickly. Very similar to 2:04 in this video, see tach in video (no affiliation): flutter_liftingoffthrottleyoutube
02-27-2024 | 06:40 PM
#623
Advanced
Joined: Feb 2022
Posts: 73
Likes: 95
From: Tucson!
Well. I ordered a oil cap because I needed to drill a hole in the current one to measure the crankcase pressure...to test out the AOS.
I discovered my current oil cap is missing an o-ring! I could hear a little leak near the cap and when I held the cap tight, it stopped.
With the new oil cap (no sound/leaks), the car seemed to idle a little better when warm. Will report back in a few days after further observation.
Now here's the main point: I got a reading of -12inH2O.
According to LN engineering, the correct reading is
COMMON CAUSES FOR LOW ENGINE VACUUM READING ON PORSCHE M9X AND LATER WATERCOOLED PORSCHE ENGINES
1. Missing engine oil cap and or oil cap O-ring.
2. Cracked or broken spark plug tubes, if applicable.
3. Disconnected or broken dipstick tube, if applicable.
4. Make sure the oil dipstick is fully seated, if applicable.
5. Anything that can leak air can leak oil and vice versa.
6. Torn AOS boot, broken or cracked oil filler tube, Dipstick and/or crankcase crossover accordion pipe.
COMMON CAUSES FOR HIGH ENGINE VACUUM READING ON PORSCHE M9X AND LATER WATERCOOLED PORSCHE ENGINES
The only thing that can cause an excessively high manometer vacuum reading is a faulty AOS and or sludge.
I discovered my current oil cap is missing an o-ring! I could hear a little leak near the cap and when I held the cap tight, it stopped.
With the new oil cap (no sound/leaks), the car seemed to idle a little better when warm. Will report back in a few days after further observation.
Now here's the main point: I got a reading of -12inH2O.
According to LN engineering, the correct reading is
- MA1 Nominal crankcase vacuum is -15.0” (-14.0” to -16.0”) of H2O (not HG).
COMMON CAUSES FOR LOW ENGINE VACUUM READING ON PORSCHE M9X AND LATER WATERCOOLED PORSCHE ENGINES
1. Missing engine oil cap and or oil cap O-ring.
2. Cracked or broken spark plug tubes, if applicable.
3. Disconnected or broken dipstick tube, if applicable.
4. Make sure the oil dipstick is fully seated, if applicable.
5. Anything that can leak air can leak oil and vice versa.
6. Torn AOS boot, broken or cracked oil filler tube, Dipstick and/or crankcase crossover accordion pipe.
COMMON CAUSES FOR HIGH ENGINE VACUUM READING ON PORSCHE M9X AND LATER WATERCOOLED PORSCHE ENGINES
The only thing that can cause an excessively high manometer vacuum reading is a faulty AOS and or sludge.
A new oil cap and rubber ring made my `15 C2S idle smoother, respond off idle better, and the stutter at 2200 rpm is largely gone. Thank you!
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02-29-2024 | 02:28 PM
#624
Burning Brakes
Joined: Sep 2012
Posts: 1,181
Likes: 189
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andredl (03-03-2024)
03-03-2024 | 10:44 AM
#625
1st Gear
Joined: Mar 2024
Posts: 1
Likes: 0
My break-in period was "by the book" as well. Mine stumbles and shakes between 2 & 3K RPM's whether hot or cold. Below 2K and above 3K, it runs beautifully. If it's driven assertively through this range, the problem is of no consequence. But gradually going through this range in a neighborhood or city street causes a significant awareness of some sort of engine anomaly. The bumping and shuttering never goes away and affects the away I have to drive it just for a smooth acceleration experience. It's very disheartening, especially since some of you indicate you have no problem at all.
Wonder if the 991.2 has these issues resolved......
Wonder if the 991.2 has these issues resolved......
Last edited by jvandenberk; 03-03-2024 at 11:06 AM.
03-03-2024 | 11:03 AM
#627
Rennlist Member
Joined: Jun 2020
Posts: 367
Likes: 214
From: Gainesville, VA
I’ve had the same issues as others with a very crude acceleration in this range with a PDK and a tune. Seems to run better in the manual mode as I’ve been playing around with this for the last months or so and there is definitely a difference between modes. Not sure why the dealers can’t confirm this and push for a fix as this has been going on for over. 10-12 or so and no one can seem to confirm and identify the cause, let alone come up with a solution. Really frustrating when you have a lot of money invested on a car that runs at these low ranges like an old carbureted Buick.
I’ve driven a lot of high end cars in my time and this is the only one that exhibits this strange behavior that no one can seem to solve.
I’ve driven a lot of high end cars in my time and this is the only one that exhibits this strange behavior that no one can seem to solve.
03-03-2024 | 01:28 PM
#629
Rennlist Member
Joined: Jan 2016
Posts: 5,309
Likes: 2,328
From: New Orleans, LA (NOLA)
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