Anyone recognize this? Shuttering under load.
Thread Starter
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Joined: Aug 2020
Posts: 130
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From: San Diego, CA
Anyone recognize this? Shuttering under load.
I have a 2010 PDK Turbo. 15k miles, no track use but did have a Cobb accessport tuner on the car at one time (no longer loaded).
During normal driving, the car accelerates as it should and shifts smoothly. When cruising on the freeway if the car downshifts from 7th to 6th (as I increase the throttle to pass another car) and the boost comes up, the car has a shuttering feeling between 2000 - 3200 RPM and then goes away. I had read on here about the VGT actuator seizing on the 997.1 cars, but they are confirmed to be operating fine on my car. The independent shops here weren't too sure what the cause is so I brought it to the local dealer. They were of the opinion it was related to the front gear drive unit or the differential as if it was slipping when under load. They changed the fluid and did a recalibration on the PDK along with a fluid flush on the gear drive unit. Both fluids were clean. For some reason they didn't do the front differential as well and I didn't realize until I was picking the car up so I may bring to the indie to check that fluid for debirs.
Everyone is pretty stumped as to what the issue is so I am coming here to see if anyone has an opinion. I spoke with CMS in Havasu and they said it might be the clutch pack in the front diff or the bearings but I would just be "trying" things. Ideally, I don't just throw a bunch of money down the drain trying to fix things that aren't broken when chasing this.
Thanks in advance!
Daniel
During normal driving, the car accelerates as it should and shifts smoothly. When cruising on the freeway if the car downshifts from 7th to 6th (as I increase the throttle to pass another car) and the boost comes up, the car has a shuttering feeling between 2000 - 3200 RPM and then goes away. I had read on here about the VGT actuator seizing on the 997.1 cars, but they are confirmed to be operating fine on my car. The independent shops here weren't too sure what the cause is so I brought it to the local dealer. They were of the opinion it was related to the front gear drive unit or the differential as if it was slipping when under load. They changed the fluid and did a recalibration on the PDK along with a fluid flush on the gear drive unit. Both fluids were clean. For some reason they didn't do the front differential as well and I didn't realize until I was picking the car up so I may bring to the indie to check that fluid for debirs.
Everyone is pretty stumped as to what the issue is so I am coming here to see if anyone has an opinion. I spoke with CMS in Havasu and they said it might be the clutch pack in the front diff or the bearings but I would just be "trying" things. Ideally, I don't just throw a bunch of money down the drain trying to fix things that aren't broken when chasing this.
Thanks in advance!
Daniel
Three Wheelin'
Joined: Mar 2017
Posts: 1,655
Likes: 490
From: Exton, PA
So they pointed to differential?
What about taking any readings, specifically misfires? Are they a possible cause for the shudder? Can you make it happen under heavy throttle lower in the gears?
Does it feel front wheels only?
When I first started reading I thought:
1. Coils
2. Sparks
3. Boost leak
However the dff comments threw me off that thought. I would definitely monitor the engine when this happens (I assume it is repeatable) and see if any cylinder is throwing a misfire. That will at least rule out the engine if you do not see them. If you do not see misfires, then you need to look elsewhere in the drivetrain. Have they focused the shudder to front/rear or all over the drivetrain?
Someone else needs to chime in, but there is a shaft that can be disconnected from the front diff, which may result in a ton of CEL's, and I am not sure I would want to run it that way at highway speeds, but that would eliminate the front diff. Do not do this on my advice, get your indy's or feedback from here or elsewhere from someone who has done this before trying it.
Ed
What about taking any readings, specifically misfires? Are they a possible cause for the shudder? Can you make it happen under heavy throttle lower in the gears?
Does it feel front wheels only?
When I first started reading I thought:
1. Coils
2. Sparks
3. Boost leak
However the dff comments threw me off that thought. I would definitely monitor the engine when this happens (I assume it is repeatable) and see if any cylinder is throwing a misfire. That will at least rule out the engine if you do not see them. If you do not see misfires, then you need to look elsewhere in the drivetrain. Have they focused the shudder to front/rear or all over the drivetrain?
Someone else needs to chime in, but there is a shaft that can be disconnected from the front diff, which may result in a ton of CEL's, and I am not sure I would want to run it that way at highway speeds, but that would eliminate the front diff. Do not do this on my advice, get your indy's or feedback from here or elsewhere from someone who has done this before trying it.
Ed
Thread Starter
Rennlist Member
Joined: Aug 2020
Posts: 130
Likes: 20
From: San Diego, CA
So they pointed to differential?
What about taking any readings, specifically misfires? Are they a possible cause for the shudder? Can you make it happen under heavy throttle lower in the gears?
Does it feel front wheels only?
When I first started reading I thought:
1. Coils
2. Sparks
3. Boost leak
However the dff comments threw me off that thought. I would definitely monitor the engine when this happens (I assume it is repeatable) and see if any cylinder is throwing a misfire. That will at least rule out the engine if you do not see them. If you do not see misfires, then you need to look elsewhere in the drivetrain. Have they focused the shudder to front/rear or all over the drivetrain?
Someone else needs to chime in, but there is a shaft that can be disconnected from the front diff, which may result in a ton of CEL's, and I am not sure I would want to run it that way at highway speeds, but that would eliminate the front diff. Do not do this on my advice, get your indy's or feedback from here or elsewhere from someone who has done this before trying it.
Ed
What about taking any readings, specifically misfires? Are they a possible cause for the shudder? Can you make it happen under heavy throttle lower in the gears?
Does it feel front wheels only?
When I first started reading I thought:
1. Coils
2. Sparks
3. Boost leak
However the dff comments threw me off that thought. I would definitely monitor the engine when this happens (I assume it is repeatable) and see if any cylinder is throwing a misfire. That will at least rule out the engine if you do not see them. If you do not see misfires, then you need to look elsewhere in the drivetrain. Have they focused the shudder to front/rear or all over the drivetrain?
Someone else needs to chime in, but there is a shaft that can be disconnected from the front diff, which may result in a ton of CEL's, and I am not sure I would want to run it that way at highway speeds, but that would eliminate the front diff. Do not do this on my advice, get your indy's or feedback from here or elsewhere from someone who has done this before trying it.
Ed
Porsche San Diego believes that it is focused to the front but I don't know how they arrived at that. I have considered disconnecting the front diff and was going to discuss with the indie shop next week when I take it in to have the fluid drained in the diff as this would rule this out rather quickly. I am consistently able to get the issue to replicate but again no fault codes.
Rennlist Member
Joined: Sep 2020
Posts: 82
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From: Orange County, CA
I had something similar when at 3/4 of WOT and it turned out that my tune was off, full WOT it didn't do it, only between 1/2 and 3/4 Did you say you removed your tune and went back to stock? Jared at BBI re-tuned my car and all stuttering is gone, he actually dialed it back a little and smoothed things out. To be clear BBI had not done the original tune on the car. They fixed me though!
Last edited by jmocporsche997; Aug 21, 2023 at 01:26 PM.
Thread Starter
Rennlist Member
Joined: Aug 2020
Posts: 130
Likes: 20
From: San Diego, CA
I had something similar when at 3/4 of WOT and it turned out that my tune was off, full WOT it didn't do it, only between 1/2 and 3/4 Did you say you removed your tune and went back to stock? Jared at BBI re-tuned my car and all stuttering is gone, he actually dialed it back a little and smoothed things out. To be clear BBI had not done the original tune on the car. They fixed me though!
Rennlist Member
Joined: Sep 2020
Posts: 82
Likes: 52
From: Orange County, CA
When I got the car a couple years ago it was tuned at about (610 torque and 597 hp rear wheel - which is what about 720 at the crank give or take - and then when I had BBI re-tune the car I said I wanted to focus on a street friendly, reliable tune (what was interesting is they first went back to stock tune, logged everything, drove it, ensured everying was fine and in great shape - then tuned) - and Jared ended up at (490 torque and 529 hp rear wheel - so about I assume about 645 at the crank) and it is sooooooo smooth and pulls so incredibly strong with peak torque at 3950 rpms. I, (like the rest of the people in the this forum) am just blown away by how amazing the 997 turbos are, I tell myself I will NEVER sell it. My car has a bunch of bolt on mods too - Europipe, Do88 Intercoolers, IPD Plenium and Y pipe and Cobb Map sensor, DSC controler, Eibach lowering sprints, Stock turbos though... Hope that ends up being your issue.
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Thread Starter
Rennlist Member
Joined: Aug 2020
Posts: 130
Likes: 20
From: San Diego, CA
When I got the car a couple years ago it was tuned at about (610 torque and 597 hp rear wheel - which is what about 720 at the crank give or take - and then when I had BBI re-tune the car I said I wanted to focus on a street friendly, reliable tune (what was interesting is they first went back to stock tune, logged everything, drove it, ensured everying was fine and in great shape - then tuned) - and Jared ended up at (490 torque and 529 hp rear wheel - so about I assume about 645 at the crank) and it is sooooooo smooth and pulls so incredibly strong with peak torque at 3950 rpms. I, (like the rest of the people in the this forum) am just blown away by how amazing the 997 turbos are, I tell myself I will NEVER sell it. My car has a bunch of bolt on mods too - Europipe, Do88 Intercoolers, IPD Plenium and Y pipe and Cobb Map sensor, DSC controler, Eibach lowering sprints, Stock turbos though... Hope that ends up being your issue.
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From: DMV
I had something similar when at 3/4 of WOT and it turned out that my tune was off, full WOT it didn't do it, only between 1/2 and 3/4 Did you say you removed your tune and went back to stock? Jared at BBI re-tuned my car and all stuttering is gone, he actually dialed it back a little and smoothed things out. To be clear BBI had not done the original tune on the car. They fixed me though!
Thread Starter
Rennlist Member
Joined: Aug 2020
Posts: 130
Likes: 20
From: San Diego, CA
Ok so an update....completely removed accessport from car. It appears that it had the stock tune with accessport loaded to be able to run gauges etc. Drive the car this morning and it is the same thing still. At freeway speeds the car shutters between 2-3k rpm in Normal mode. In sport mode the car doesn't appear to have the issue but I didn't have enough time this morning on my drive to work. We will see today.
The plot thickens.
The plot thickens.
Three Wheelin'
Joined: Mar 2017
Posts: 1,655
Likes: 490
From: Exton, PA
Well it's probably directly unrelated, but I had a dirty MAF that was causing idle issues that would disappear in Sport mode.....but that was at idle, not at speed.
Have you logged any data points when this is happening?
Ed
Have you logged any data points when this is happening?
Ed
Thread Starter
Rennlist Member
Joined: Aug 2020
Posts: 130
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From: San Diego, CA
Interesting. When you say logged data points do you mean through a diagnostic tool or just noted driving experiences?
Three Wheelin'
Joined: Mar 2017
Posts: 1,655
Likes: 490
From: Exton, PA
Tool. I used Durametric to see the MAF showing an out of whack response when the engine would stutter.
I used a tool to display the results as a graph.. but my old brain is having trouble finding it. I'll keep looking and post back when I find it (visually it was much easier to see the problem).
I think it was Meta something.... ugh. Hopefully it wasn't on my old laptop.
Ed
I used a tool to display the results as a graph.. but my old brain is having trouble finding it. I'll keep looking and post back when I find it (visually it was much easier to see the problem).
I think it was Meta something.... ugh. Hopefully it wasn't on my old laptop.
Ed
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*Edit: I, and many others here on the forum, use the Accessport for data logging quite a bit.
Last edited by truekraut; Aug 23, 2023 at 02:34 PM.
Thread Starter
Rennlist Member
Joined: Aug 2020
Posts: 130
Likes: 20
From: San Diego, CA
Since you have the COBB Accessport, you can run a data log to see what’s going on while under load. Typically, second to third gear pulls at WOT are what’s used to look at timing, AFR, short and long term fuel trims, and a plethora of other parameters. I don’t think it’s a comprehensive as something like PIWIS, but it definitely provides enough information to get an idea of whether something is off.
*Edit: I, and many others here on the forum, use the Accessport for data logging quite a bit.
*Edit: I, and many others here on the forum, use the Accessport for data logging quite a bit.
Tool. I used Durametric to see the MAF showing an out of whack response when the engine would stutter.
I used a tool to display the results as a graph.. but my old brain is having trouble finding it. I'll keep looking and post back when I find it (visually it was much easier to see the problem).
I think it was Meta something.... ugh. Hopefully it wasn't on my old laptop.
Ed
I used a tool to display the results as a graph.. but my old brain is having trouble finding it. I'll keep looking and post back when I find it (visually it was much easier to see the problem).
I think it was Meta something.... ugh. Hopefully it wasn't on my old laptop.
Ed