991.1 stumble/hesitation
#31
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Same thing here .. I had hesitation on start and Stumble at 2800 rpm 991.1 4s. I had to change my variocam solenoid and valve lift solenoid on cylinders 4-5-6 due to many missfires. After reading several posts here I believe the two are related. The car is much better since the 2 solenoid changed (especially at the start at low rpm hesitation almost over ) I wonder if these two parts can be tested to see their proper functioning?
Last edited by __ Charley __; 09-06-2021 at 07:05 PM.
#32
Burning Brakes
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I started a thread a while ago concerning the variocam solenoid and I have noticed a number of posts since reporting low speed stumble with a smoother high speed performance - all symptoms of failure of this part.
BMW considers the corresponding part in their engines to be a wear item - like a spark plug - and recommends replacement at around 80k.
I am starting to wonder if Porsche knows (and knew) about the limited life of this part and decided not to include it in regular maintenance for the purpose of lowering the projected cost of maintenance.
BMW considers the corresponding part in their engines to be a wear item - like a spark plug - and recommends replacement at around 80k.
I am starting to wonder if Porsche knows (and knew) about the limited life of this part and decided not to include it in regular maintenance for the purpose of lowering the projected cost of maintenance.
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__ Charley __ (09-08-2021)
#33
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Interesting point!I will porbably end changing all of 4.. Hoping that is stumble hesitation and rough idle related... Maybe somemone already did that..?
But car run a lot better since 2 of them are New..!!
But car run a lot better since 2 of them are New..!!
#34
Track Day
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My new to me 15 C2S was a bit stumbly and was not that impressive when romping on it when I took delivery. CPO car so just had the major service. As Ive driven the car harder, its came to life. I know the dealer had it for 38 days for sale, so its probably sat awhile. Maintained at Porsche Ft Myers its whole life as well. Makes me realize just how much these cars beg to be driven and driven hard. Coming from M cars, they're the exact same way. Never had a hesitation though, just rather lazy. The good thing is I have a VP Racing gas station next to my house that has no ethanol 93 as well as racing fuel of all levels. Ran their 97 on my tuned M6 GC with great results. Not sure how these motors respond to that octane but Ill be using their 93 for sure
Last edited by slo_991; 11-07-2021 at 01:17 AM. Reason: Grammer
#35
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Had a stumble on my 911-991.1 that my OPC fixed yesterday. My 911 was showing all these signs...
slight hesitancy at low RPM, most obvs in second and third gear
feels like the engine 'gets lost' for a short time at low or lug rpm... around 1.5k to 2k RPM, pauses for a second then..
feels like you run over a small pot hole when you accelerate
almost feels like a mis fire, but it isnt
The fault was a failing PADM mount. I eventually found this out because the PADM warning light eventually came on about 3 months later, so the OPC replaced the mount and this also fixed the stumble at the same time. They were already aware that the PADM and the stumble would be related as its the failed electronic mount that causes the stumble.
So if you have a 911.1 with Sport /Sport + then a failing PADM is a common issue and might be the reason why you are feeling the engine stumble at 1.5 to 2.5k RPM.
Its 100% fixed mine
so thank you OPC
slight hesitancy at low RPM, most obvs in second and third gear
feels like the engine 'gets lost' for a short time at low or lug rpm... around 1.5k to 2k RPM, pauses for a second then..
feels like you run over a small pot hole when you accelerate
almost feels like a mis fire, but it isnt
The fault was a failing PADM mount. I eventually found this out because the PADM warning light eventually came on about 3 months later, so the OPC replaced the mount and this also fixed the stumble at the same time. They were already aware that the PADM and the stumble would be related as its the failed electronic mount that causes the stumble.
So if you have a 911.1 with Sport /Sport + then a failing PADM is a common issue and might be the reason why you are feeling the engine stumble at 1.5 to 2.5k RPM.
Its 100% fixed mine
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#36
Rennlist Member
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Had a stumble on my 911-991.1 that my OPC fixed yesterday. My 911 was showing all these signs...
slight hesitancy at low RPM, most obvs in second and third gear
feels like the engine 'gets lost' for a short time at low or lug rpm... around 1.5k to 2k RPM, pauses for a second then..
feels like you run over a small pot hole when you accelerate
almost feels like a mis fire, but it isnt
The fault was a failing PADM mount. I eventually found this out because the PADM warning light eventually came on about 3 months later, so the OPC replaced the mount and this also fixed the stumble at the same time. They were already aware that the PADM and the stumble would be related as its the failed electronic mount that causes the stumble.
So if you have a 911.1 with Sport /Sport + then a failing PADM is a common issue and might be the reason why you are feeling the engine stumble at 1.5 to 2.5k RPM.
Its 100% fixed mine
so thank you OPC
slight hesitancy at low RPM, most obvs in second and third gear
feels like the engine 'gets lost' for a short time at low or lug rpm... around 1.5k to 2k RPM, pauses for a second then..
feels like you run over a small pot hole when you accelerate
almost feels like a mis fire, but it isnt
The fault was a failing PADM mount. I eventually found this out because the PADM warning light eventually came on about 3 months later, so the OPC replaced the mount and this also fixed the stumble at the same time. They were already aware that the PADM and the stumble would be related as its the failed electronic mount that causes the stumble.
So if you have a 911.1 with Sport /Sport + then a failing PADM is a common issue and might be the reason why you are feeling the engine stumble at 1.5 to 2.5k RPM.
Its 100% fixed mine
![Smilie](https://rennlist.com/forums/images/smilies/smile.gif)
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GermanCarFan1 (05-11-2023)
#38
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I had a terrible stumble exactly as described here. I had no idea it was a thing, but I ended up tracking it down to the actual acceleration pedal in my case. Replacing the pedal and pedal travel sensor my issue has been cleared up. Putting the old pedal on and it comes right back. Hope that helps someone?
#39
Three Wheelin'
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I had a terrible stumble exactly as described here. I had no idea it was a thing, but I ended up tracking it down to the actual acceleration pedal in my case. Replacing the pedal and pedal travel sensor my issue has been cleared up. Putting the old pedal on and it comes right back. Hope that helps someone?
#40
Nordschleife Master
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As a data point, I have installed a Sprint Booster which increases pedal response but I still have the stumble, but not all the time.
#41
Three Wheelin'
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Received the 2016 GT4 throttle pedal a few days ago. My cul-de-sac is still half snow/ice, but I decided to get the car out yesterday regardless. I knew there was a reason I got these crappy all-season tires ![Smilie](https://rennlist.com/forums/images/smilies/smile.gif)
I drove it yesterday with the original throttle. Definitely, some stumble/hesitation as I typically find on most drives. I then parked back in the garage and swapped the throttle pedals out (easy job, other than I am extremely good at breaking clips, which I ended up doing with the sensor clip). I did the throttle reset procedure as I figured that might be a good step.
Today, I drove the car for about an hour. I could not reproduce the stumble in any way, shape or form no matter what I tried.
Only time will tell of course, but that was one of the most enjoyable drives I've ever had in the nearly 6 years that I've owned my 911.
![Smilie](https://rennlist.com/forums/images/smilies/smile.gif)
I drove it yesterday with the original throttle. Definitely, some stumble/hesitation as I typically find on most drives. I then parked back in the garage and swapped the throttle pedals out (easy job, other than I am extremely good at breaking clips, which I ended up doing with the sensor clip). I did the throttle reset procedure as I figured that might be a good step.
Today, I drove the car for about an hour. I could not reproduce the stumble in any way, shape or form no matter what I tried.
Only time will tell of course, but that was one of the most enjoyable drives I've ever had in the nearly 6 years that I've owned my 911.
#42
Track Day
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Received the 2016 GT4 throttle pedal a few days ago. My cul-de-sac is still half snow/ice, but I decided to get the car out yesterday regardless. I knew there was a reason I got these crappy all-season tires ![Smilie](https://rennlist.com/forums/images/smilies/smile.gif)
I drove it yesterday with the original throttle. Definitely, some stumble/hesitation as I typically find on most drives. I then parked back in the garage and swapped the throttle pedals out (easy job, other than I am extremely good at breaking clips, which I ended up doing with the sensor clip). I did the throttle reset procedure as I figured that might be a good step.
Today, I drove the car for about an hour. I could not reproduce the stumble in any way, shape or form no matter what I tried.
Only time will tell of course, but that was one of the most enjoyable drives I've ever had in the nearly 6 years that I've owned my 911.
![Smilie](https://rennlist.com/forums/images/smilies/smile.gif)
I drove it yesterday with the original throttle. Definitely, some stumble/hesitation as I typically find on most drives. I then parked back in the garage and swapped the throttle pedals out (easy job, other than I am extremely good at breaking clips, which I ended up doing with the sensor clip). I did the throttle reset procedure as I figured that might be a good step.
Today, I drove the car for about an hour. I could not reproduce the stumble in any way, shape or form no matter what I tried.
Only time will tell of course, but that was one of the most enjoyable drives I've ever had in the nearly 6 years that I've owned my 911.
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koala (05-12-2023)
#43
Three Wheelin'
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That is amazing! Glad swapping out the pedal helped you as well. I changed the solenoids a year or two ago (can't remember how long it's been), and I don't think they helped my specific issue other than maybe a bit of placebo effect. That said, they are a replaceable / wear item on some other car brands so I don't feel like it was money wasted.
edit - I mentioned this in another thread, but I've had virtually zero stumble/hesitation ever since I swapped the throttle out. It appears to have been the solution for this issue. Solenoids and throttle body replacement both didn't solve it for me.
edit - I mentioned this in another thread, but I've had virtually zero stumble/hesitation ever since I swapped the throttle out. It appears to have been the solution for this issue. Solenoids and throttle body replacement both didn't solve it for me.
Last edited by koala; 05-12-2023 at 02:33 PM.
#44
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Received the 2016 GT4 throttle pedal a few days ago. My cul-de-sac is still half snow/ice, but I decided to get the car out yesterday regardless. I knew there was a reason I got these crappy all-season tires ![Smilie](https://rennlist.com/forums/images/smilies/smile.gif)
I drove it yesterday with the original throttle. Definitely, some stumble/hesitation as I typically find on most drives. I then parked back in the garage and swapped the throttle pedals out (easy job, other than I am extremely good at breaking clips, which I ended up doing with the sensor clip). I did the throttle reset procedure as I figured that might be a good step.
Today, I drove the car for about an hour. I could not reproduce the stumble in any way, shape or form no matter what I tried.
Only time will tell of course, but that was one of the most enjoyable drives I've ever had in the nearly 6 years that I've owned my 911.
![Smilie](https://rennlist.com/forums/images/smilies/smile.gif)
I drove it yesterday with the original throttle. Definitely, some stumble/hesitation as I typically find on most drives. I then parked back in the garage and swapped the throttle pedals out (easy job, other than I am extremely good at breaking clips, which I ended up doing with the sensor clip). I did the throttle reset procedure as I figured that might be a good step.
Today, I drove the car for about an hour. I could not reproduce the stumble in any way, shape or form no matter what I tried.
Only time will tell of course, but that was one of the most enjoyable drives I've ever had in the nearly 6 years that I've owned my 911.
This is great news! Has it held up since?
#45
Rennlist Member
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My 2013 991.1 Carrera S with PDK started the hesitation/stumble thing about 6 weeks ago at 87,000km. For me it happens when under excelleration under 3500 rpm. Took it to the dealer who ran all the tests you can imagine only to say the car shows nothing is wrong. They do admit to feeling the issue though. After reading this thread (glad to see I'm not alone) I've gone ahead and ordered a new (well, slightly used) throttle pedal. I figured for $65 it's worth a try.
I have owed the car for 3 years now (since 61,000km) and had zero issues until now. For the average person, I doubt they would even notice, (some might say, what I feel is normal) but for us, we all know this isn't normal.
Once I have had a chance to install and test I will report back. eBay says two weeks for delivery. Unitl then.....
I have owed the car for 3 years now (since 61,000km) and had zero issues until now. For the average person, I doubt they would even notice, (some might say, what I feel is normal) but for us, we all know this isn't normal.
Once I have had a chance to install and test I will report back. eBay says two weeks for delivery. Unitl then.....