Engine stumble/hesitation around 2500 RPM?
#587
04-21-2016, 07:01 AM
Update: I brought my car into what is probably the best local Porsche mechanic in the area. This guy has had his Porsche shop for 28 years. He wins local races. He's the real deal.
First I drove, and then we switched and he drove back. When I drove he was watching for my shift points, any possible lugging of the engine, etc. I was able to replicate the stumble and describe when I feel it, at what RPMs, etc. He said I was shifting just fine (not "driving it wrong" as the PCNA tech said). When he drove it he said he did indeed feel it. He thought it could be a combination of lifter changes and possible sticking throttle body. His idea is to clean the throttle body and go from there. I know there has been a throttle body replacement with someone here with *no* improvement in the stumble, but we're just charting a course for investigation. He's the first mechanic to take me seriously and start to lay out a plan.
Overall, it was a great car day. The weather was perfect, and I was able to get someone else to feel it so I know I'm not going crazy or just "driving it wrong". Yes, I'm still bitter at PCNA for telling me that.
First I drove, and then we switched and he drove back. When I drove he was watching for my shift points, any possible lugging of the engine, etc. I was able to replicate the stumble and describe when I feel it, at what RPMs, etc. He said I was shifting just fine (not "driving it wrong" as the PCNA tech said). When he drove it he said he did indeed feel it. He thought it could be a combination of lifter changes and possible sticking throttle body. His idea is to clean the throttle body and go from there. I know there has been a throttle body replacement with someone here with *no* improvement in the stumble, but we're just charting a course for investigation. He's the first mechanic to take me seriously and start to lay out a plan.
Overall, it was a great car day. The weather was perfect, and I was able to get someone else to feel it so I know I'm not going crazy or just "driving it wrong". Yes, I'm still bitter at PCNA for telling me that.
#588
04-21-2016, 07:20 AM
Wow great, hope you get this diagnosed properly. Sounds like you found the right guy to get this fixed.
PCNA really dropped the ball on this one. Really sucks.
PCNA really dropped the ball on this one. Really sucks.
#589
04-27-2016, 01:00 PM
As was predicted here, the stumble is back on my car. In fact, it may be worse than it's ever been. It has actually stumbled several times "big time" above 3K RPMs for the first time ever. It feels like it loses power, dives down and picks back up. I've called the dealer to make them aware.
Also, since the S/W was loaded, I'm experiencing a "surprising" very hard shift from the PDK on an occasional basis with no rhyme nor reason. It can be from any gear to any gear and doesn't matter if it's sport, sport-plus or normal mode.
This is all very disturbing and is starting to affect the way I now have to drive this car. I cannot move through the 2 - 3K RPM range without it stumbling and tugging, and occasionally hopping.
I'm open to anything that anyone learns that might help me through this. The warranty expires in November and I don't want to have to live with this problem and the potentially inevitable part failure.
Other than these issues, the car has been solid, so I'm very disappointed in all this.
Also, since the S/W was loaded, I'm experiencing a "surprising" very hard shift from the PDK on an occasional basis with no rhyme nor reason. It can be from any gear to any gear and doesn't matter if it's sport, sport-plus or normal mode.
This is all very disturbing and is starting to affect the way I now have to drive this car. I cannot move through the 2 - 3K RPM range without it stumbling and tugging, and occasionally hopping.
I'm open to anything that anyone learns that might help me through this. The warranty expires in November and I don't want to have to live with this problem and the potentially inevitable part failure.
Other than these issues, the car has been solid, so I'm very disappointed in all this.
I've had the stumble since the beginning. I took my car to the dealer a few weeks ago for the annual oil change, brake flush, etc. and asked them to check for any S/W updates. There were many. I was mostly interested in the DME update being discussed here, and it was available for my car.
After installation, I can conclusively say that my problem is 75% eliminated. The other 25% I can still lightly feel the stumbling effect, but it has greatly diminished. It seems that the update moved the RPM range for my issue from the broad range of 2K - 3K down to about 2.2k thru 2.6K. Even then, when its there, it's not as severe as before. I have noticed that when the engine is cold and I happen to change from 1st to 2nd when it enters that range, it bucks and jumps a little. But, it did this in the broader range before as well. After it's warmed up, it settles down.
The reason I know it's improved is this: Driving it a couple of days ago with the stereo turned up loud, I realized that I was moving along with the car still in 3rd gear with the RPM's gradually increasing within the original broad stumbling range, and it was running very smoothly.
In summary, let me say that this has improved my car greatly. Is it possible that the DME may adjust something through adaptations that will bring the stumbling back? I guess only time will tell.
One thing did change on my car. The PDK tranny seems to change gears a lot harder now than it did before. In Normal mode, sometimes during the changes between 1st, 2nd, and 3rd, it really changes hard. It feels almost like it's in Sport or Sport+ mode and the electronic engine mounts are activated. I mentioned this to the dealer, but they didn't have any answers. Anyone else experiencing this change?
After installation, I can conclusively say that my problem is 75% eliminated. The other 25% I can still lightly feel the stumbling effect, but it has greatly diminished. It seems that the update moved the RPM range for my issue from the broad range of 2K - 3K down to about 2.2k thru 2.6K. Even then, when its there, it's not as severe as before. I have noticed that when the engine is cold and I happen to change from 1st to 2nd when it enters that range, it bucks and jumps a little. But, it did this in the broader range before as well. After it's warmed up, it settles down.
The reason I know it's improved is this: Driving it a couple of days ago with the stereo turned up loud, I realized that I was moving along with the car still in 3rd gear with the RPM's gradually increasing within the original broad stumbling range, and it was running very smoothly.
In summary, let me say that this has improved my car greatly. Is it possible that the DME may adjust something through adaptations that will bring the stumbling back? I guess only time will tell.
One thing did change on my car. The PDK tranny seems to change gears a lot harder now than it did before. In Normal mode, sometimes during the changes between 1st, 2nd, and 3rd, it really changes hard. It feels almost like it's in Sport or Sport+ mode and the electronic engine mounts are activated. I mentioned this to the dealer, but they didn't have any answers. Anyone else experiencing this change?
#590
04-27-2016, 03:17 PM
#591
04-27-2016, 03:58 PM
At this point, I simply try to grin and bear it. Fortunately, after 3 years of ownership, the car continues to provide copious amounts of grins.
One concern though, is the possibility of diminished value if one were attempting to sell to a private party. If I were in the market for a private sale used 991 and actually felt it stumble during a test drive, I think I'd probably look elsewhere. An even worse scenario would be for the new buyer to give you a call a couple of weeks after the sale and ask what's wrong with the car.
I've always opted for the trade-in route so I guess it's a moot point (unless the dealer were to low ball the trade value due to the stumble)
One concern though, is the possibility of diminished value if one were attempting to sell to a private party. If I were in the market for a private sale used 991 and actually felt it stumble during a test drive, I think I'd probably look elsewhere. An even worse scenario would be for the new buyer to give you a call a couple of weeks after the sale and ask what's wrong with the car.
I've always opted for the trade-in route so I guess it's a moot point (unless the dealer were to low ball the trade value due to the stumble)
#594
04-27-2016, 09:39 PM
Registered User
Join Date: Aug 2015
Location: Dickson TN
Age: 54
Posts: 103
Rep Power: 13 
I've put about 500 miles on the car since my latest update and all is still well.
Stumble free and the PDK in all modes (including manual mode) is smooth as butter.
I'm going to hit the mountains of GA/NC/TN this weekend and will report back after some hard runs.
2013 C4S PDK here.
Stumble free and the PDK in all modes (including manual mode) is smooth as butter.
I'm going to hit the mountains of GA/NC/TN this weekend and will report back after some hard runs.
2013 C4S PDK here.
#595
04-28-2016, 05:42 AM
It has a very occasional and different feeling stumble, but it happens.My point though is that I also bought a BMW 340i (6-speed) last year that is my DD, and it has a horrible stumble. I started a thread on it on one forum because I've been around the block a few times and I know that if "they all do that" there's no point in taking it into the dealer. Several other people have noted the same symptom. It's a software thing, I'm sure. In this case, I think it's got to do with emissions, maybe preheating the cats, as it only happens in the first minute or so of driving. But it's pretty severe and annoying, especially to those of us who are card-carrying members of the OCD society.
So yes, it's great that we have these Internet resources to support each other and maybe find a solution, work-around, or a way to reduce the severity. These days, these cars are so heavily controlled by computers that run based on sensor signals that I honestly feel sorry for the mechanics who have to try to resolve these kinds of drivability issues. Especially since none of us have access to (nor likely the skills to change) the code that runs the cars.
I'm giving serious thought to buying a Tesla next. They are not problem-free either, but at least it appears that Tesla makes a sincere effort to resolve issues quickly, and they download software updates automagically as soon as they are released.
#596
04-28-2016, 08:07 AM
Update: I brought my car into what is probably the best local Porsche mechanic in the area. This guy has had his Porsche shop for 28 years. He wins local races. He's the real deal.
First I drove, and then we switched and he drove back. When I drove he was watching for my shift points, any possible lugging of the engine, etc. I was able to replicate the stumble and describe when I feel it, at what RPMs, etc. He said I was shifting just fine (not "driving it wrong" as the PCNA tech said). When he drove it he said he did indeed feel it. He thought it could be a combination of lifter changes and possible sticking throttle body. His idea is to clean the throttle body and go from there. I know there has been a throttle body replacement with someone here with *no* improvement in the stumble, but we're just charting a course for investigation. He's the first mechanic to take me seriously and start to lay out a plan.
Overall, it was a great car day. The weather was perfect, and I was able to get someone else to feel it so I know I'm not going crazy or just "driving it wrong". Yes, I'm still bitter at PCNA for telling me that.
First I drove, and then we switched and he drove back. When I drove he was watching for my shift points, any possible lugging of the engine, etc. I was able to replicate the stumble and describe when I feel it, at what RPMs, etc. He said I was shifting just fine (not "driving it wrong" as the PCNA tech said). When he drove it he said he did indeed feel it. He thought it could be a combination of lifter changes and possible sticking throttle body. His idea is to clean the throttle body and go from there. I know there has been a throttle body replacement with someone here with *no* improvement in the stumble, but we're just charting a course for investigation. He's the first mechanic to take me seriously and start to lay out a plan.
Overall, it was a great car day. The weather was perfect, and I was able to get someone else to feel it so I know I'm not going crazy or just "driving it wrong". Yes, I'm still bitter at PCNA for telling me that.
#597
04-28-2016, 10:10 AM
Not done yet - I have my 3 year service coming up next month so we agreed I would just bring it in there and he would also clean the throttle body at the same time he was doing other maintenance items.
#598
05-02-2016, 10:18 AM
Registered User
Join Date: Aug 2015
Location: Dickson TN
Age: 54
Posts: 103
Rep Power: 13 I've put about 500 miles on the car since my latest update and all is still well.
Stumble free and the PDK in all modes (including manual mode) is smooth as butter.
I'm going to hit the mountains of GA/NC/TN this weekend and will report back after some hard runs.
2013 C4S PDK here.
Stumble free and the PDK in all modes (including manual mode) is smooth as butter.
I'm going to hit the mountains of GA/NC/TN this weekend and will report back after some hard runs.
2013 C4S PDK here.
#600
06-13-2016, 08:23 AM
http://rennlist.com/forums/991/93914...ollection.html
Please add your info if you can. Thanks!
Edit: or here: https://www.6speedonline.com/forums/...ollection.html
Please add your info if you can. Thanks!
Edit: or here: https://www.6speedonline.com/forums/...ollection.html
Last edited by stealthboy; 06-13-2016 at 10:19 AM.