981S - Acceleration not very smooth - is this normal?
#31
sorry brother I have to disagree with you here.
I know there’s another issue with the dead stop stall…and guess what? I had that on my 991.1S.
it was scary and annoying as hell. My heart sank every time the car did that. It was unpredictable.
this is a diff FEELING.
no stalling. It’s not a dip in the torque curve.
it’s a lack of smoothness at specific RPM points.
My buddy has a 991.1S….i drove it and it’s smooth.
so I am not making things up here. and I certainly know the diff.
either way my car is better after the oil cap.
So maybe it’s related to crankcase pressure. Mine is still low by 2 mmH2O
and I can still hear a little pop sometimes at 2800 …
I know there’s another issue with the dead stop stall…and guess what? I had that on my 991.1S.
it was scary and annoying as hell. My heart sank every time the car did that. It was unpredictable.
this is a diff FEELING.
no stalling. It’s not a dip in the torque curve.
it’s a lack of smoothness at specific RPM points.
My buddy has a 991.1S….i drove it and it’s smooth.
so I am not making things up here. and I certainly know the diff.
either way my car is better after the oil cap.
So maybe it’s related to crankcase pressure. Mine is still low by 2 mmH2O
and I can still hear a little pop sometimes at 2800 …
I wasn't aware that there was another issue with a similar type behavior. People have bitching online and making YT videos showing the PDK dead stop thing for more than a decade for both the 981 and 991 models, so I assumed that is what was going on here as well, but thanks for the additional info
Last edited by ICNU; 10-30-2023 at 08:04 AM.
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Sajan (10-31-2023)
#32
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Check your High Pressure Fuel Pump. Mine was dying and it was very similar feel to what OP described. Uneven acceleration, torque drops in 3-4k range, random misfiers under acceleration (check OBD errors). It was all very random, and not every time. But it got worse over may be 6 months, so I started digging and HPFP replacement fixed everything.
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#33
Pro
Thread Starter
I certainly cant disagree with your personal experience, especially since you have also experienced the dead stop hesitation. I have no reason to doubt you if say this is indeed different. My 981 was my first PDK equipped car and I noticed dead stop hesitation immediately, and like you say, it was frightening in some scenarios. Trying to move over quickly into an adjacent lane from a dead stop behind a stopped vehicle, and traffic in that lane coming at you fast was flat out scary as the car wouldn't move for a fraction of a second before moving, and by that time the other cars are right on top of you.
I wasn't aware that there was another issue with a similar type behavior. People have bitching online and making YT videos showing the PDK dead stop thing for more than a decade for both the 981 and 991 models, so I assumed that is what was going on here as well, but thanks for the additional info
I wasn't aware that there was another issue with a similar type behavior. People have bitching online and making YT videos showing the PDK dead stop thing for more than a decade for both the 981 and 991 models, so I assumed that is what was going on here as well, but thanks for the additional info
issue 1: "stall" from a dead stop. it's like the clutch slips or something. you give gas, car revs up and starts going and boom, just stalls for a second and it goes. i learned to compensate for it by rolling a sec before going..
that was on the 991. i don't have that issue at all.
issue: 2 to 3.5K range...slight gas under load and as the rpm is climbing, you feel this slight tug/pop/stumble feeling....
Check your High Pressure Fuel Pump. Mine was dying and it was very similar feel to what OP described. Uneven acceleration, torque drops in 3-4k range, random misfiers under acceleration (check OBD errors). It was all very random, and not every time. But it got worse over may be 6 months, so I started digging and HPFP replacement fixed everything.
no codes though.
I did notice the symptoms were non-existent at high altitude...
#34
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Ya the two issues get mixed and maybe rightfully so......because the cause is still unknown.
issue 1: "stall" from a dead stop. it's like the clutch slips or something. you give gas, car revs up and starts going and boom, just stalls for a second and it goes. i learned to compensate for it by rolling a sec before going..
that was on the 991. i don't have that issue at all.
issue: 2 to 3.5K range...slight gas under load and as the rpm is climbing, you feel this slight tug/pop/stumble feeling....
It very well could be. whenever I logged data on PIWIS for HPFP, it showed tiny dips in pressure around the same time I felt these little misfires. I don't know if the dips are because of "pause" in the engine itself though..cause or symptom? hm
no codes though.
I did notice the symptoms were non-existent at high altitude...
issue 1: "stall" from a dead stop. it's like the clutch slips or something. you give gas, car revs up and starts going and boom, just stalls for a second and it goes. i learned to compensate for it by rolling a sec before going..
that was on the 991. i don't have that issue at all.
issue: 2 to 3.5K range...slight gas under load and as the rpm is climbing, you feel this slight tug/pop/stumble feeling....
It very well could be. whenever I logged data on PIWIS for HPFP, it showed tiny dips in pressure around the same time I felt these little misfires. I don't know if the dips are because of "pause" in the engine itself though..cause or symptom? hm
no codes though.
I did notice the symptoms were non-existent at high altitude...
#35
Pro
Thread Starter
Forgot to close the loop on this thread.
This is resolved for the most part!
It's been about 2 months I believe, but during my troubleshooting process..I decided to test the crankcase pressure.
I ordered a new oil cap so I could drill my old one. I just happened to compare them and noticed an o-ring was missing on my old one. Turns out this was causing some crankcase pressure loss. about 1+ mmH20.
This is probably what I was feeling. With the new cap, the car drives great!
I definitely feel a huge improvement. It was a bit frustrating to drive under 3K. Car just felt sluggish and "slowly" climbed up ...stumbling along the way.
Now it just goes. And if I feel a tiny little pop or stumble, it's so instantaneous I don't think much of it. You would have to go out of your way feeling for it, which I have to untrain myself to do after trying to diagnose it for months.
The little stutters I felt are most likely transition points or something for the variocam...and now they are much quicker and imperceptible.
Wasted money on a bunch of crap I didn't need to but hey at least now I have replaced:
spark plugs, coils, crankcase sensor, camshaft sensor, camshaft solenoids, throttle pedal..
This is resolved for the most part!
It's been about 2 months I believe, but during my troubleshooting process..I decided to test the crankcase pressure.
I ordered a new oil cap so I could drill my old one. I just happened to compare them and noticed an o-ring was missing on my old one. Turns out this was causing some crankcase pressure loss. about 1+ mmH20.
This is probably what I was feeling. With the new cap, the car drives great!
I definitely feel a huge improvement. It was a bit frustrating to drive under 3K. Car just felt sluggish and "slowly" climbed up ...stumbling along the way.
Now it just goes. And if I feel a tiny little pop or stumble, it's so instantaneous I don't think much of it. You would have to go out of your way feeling for it, which I have to untrain myself to do after trying to diagnose it for months.
The little stutters I felt are most likely transition points or something for the variocam...and now they are much quicker and imperceptible.
Wasted money on a bunch of crap I didn't need to but hey at least now I have replaced:
spark plugs, coils, crankcase sensor, camshaft sensor, camshaft solenoids, throttle pedal..
The following 3 users liked this post by Sajan:
#36
Thanks for following up on this. Always good to have a resolution to a problem for others to find should they need it. Any chance you snapped a pic of the old one w/ the missing o-ring vs the new one so people have a visual ?
#37
Burning Brakes
That's pretty nuts: glad you found it. Vacuum leaks are a common source of problems, but it's pretty rare for one to be big enough to cause running issues but small enough not to throw codes!
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Sajan (12-27-2023)
#38
Pro
Thread Starter
I tested it without the o-ring. look at reading.
then held it tight, reading goes up. so there was def a leak.
then held it tight, reading goes up. so there was def a leak.
Last edited by Sajan; 12-27-2023 at 12:51 PM.
The following 2 users liked this post by Sajan:
IndigoInkTaco (12-27-2023),
Larson E. Rapp (12-28-2023)
#40
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Thread Starter
#41
#42
@Sajan whats the part number on your new cap?
@davecramer made me curious so I went and looked at mine and I also don't have an o-ring on there. I'm assuming any o-ring that expands to 80mm (OD) and probably a 76mm (ID) will work as long as it's oil/fuel resistant.
@davecramer made me curious so I went and looked at mine and I also don't have an o-ring on there. I'm assuming any o-ring that expands to 80mm (OD) and probably a 76mm (ID) will work as long as it's oil/fuel resistant.
#43
Now I'm really curious. This isn't an o-ring that would just fall off during an oil change and I doubt any tech would remove it. And certainly not so many, as we just found out on a quick random sample lol.
I wonder if this is something Porsche updated along the way. I see my part number (981.107.035.06) is discontinued. Looks like the new part number is (981-107-035-08).
https://parts.porschechandler.com/oe...bC1oNi1nYXM%3D
I wonder if this is something Porsche updated along the way. I see my part number (981.107.035.06) is discontinued. Looks like the new part number is (981-107-035-08).
https://parts.porschechandler.com/oe...bC1oNi1nYXM%3D
Last edited by IndigoInkTaco; 12-29-2023 at 10:02 PM.
#44
Pro
Thread Starter
@Sajan whats the part number on your new cap?
@davecramer made me curious so I went and looked at mine and I also don't have an o-ring on there. I'm assuming any o-ring that expands to 80mm (OD) and probably a 76mm (ID) will work as long as it's oil/fuel resistant.
@davecramer made me curious so I went and looked at mine and I also don't have an o-ring on there. I'm assuming any o-ring that expands to 80mm (OD) and probably a 76mm (ID) will work as long as it's oil/fuel resistant.
Now I'm really curious. This isn't an o-ring that would just fall off during an oil change and I doubt any tech would remove it. And certainly not so many, as we just found out on a quick random sample lol.
I wonder if this is something Porsche updated along the way. I see my part number (981.107.035.06) is discontinued. Looks like the new part number is (981-107-035-08).
https://parts.porschechandler.com/oe...bC1oNi1nYXM%3D
I wonder if this is something Porsche updated along the way. I see my part number (981.107.035.06) is discontinued. Looks like the new part number is (981-107-035-08).
https://parts.porschechandler.com/oe...bC1oNi1nYXM%3D