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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 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
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.
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
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....
Originally Posted by t-design
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.
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...
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...
The misfires will show as errors in OBD tools, so you won't have to guess
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..
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 ?
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!
@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).
@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.
981-107-035-08 Filler Cap $23.93
Originally Posted by IndigoInkTaco
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).
10-30-2023, 07:59 AM
