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Engine stumble/hesitation around 2500 RPM?

 
  #106  
Old 08-05-2014, 10:48 AM
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Originally Posted by Money2536 View Post
I was deathly afraid of something like this happening to my $135,000 car. My car has been getting progressively worse. This is the first time in my life that I wished something would just break. What I don't want to do is play the taking it to the dealership game over and over again.
Hopefully they don't try blaming this on your obsessive detailing! Maybe the car is always too clean and looking good? All joking aside, please keep us posted. These type of problems are always concerning. Especially how they get handled and resolved.
 
  #107  
Old 08-05-2014, 10:54 AM
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Haha. I told them about 15 times to absolutely, positively not wash my car. They have a swirled out $200,000 Turbo S convertible in the showroom.
 
  #108  
Old 08-05-2014, 10:57 AM
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The only other times that I've experienced this type of stumble in other (older) cars, it was either due to a defective vacuum line or a timing issue.
In this case my engine seems to be starved of fuel at exactly 2500rpm and isn't even an intermittent problem that they can't replicate.

I'm hoping one of us finds a competent mechanic who is not solely reliant on codes.
 

Last edited by dux; 08-05-2014 at 10:58 AM. Reason: typo
  #109  
Old 08-05-2014, 10:59 AM
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Originally Posted by Money2536 View Post
Haha. I told them about 15 times to absolutely, positively not wash my car. They have a swirled out $200,000 Turbo S convertible in the showroom.
They think I'm nuts too. I repeat it like 5 times. Just bought my preowned 991 and they had fine nothing but wash it. They don't "detail" it until it sells. I told them not to touch it. They delivered it to me untouched, and didn't even take the window stickers off! Thank goodness!

Not surprising about the Turbo S. You talk to them about swirling and paint correction and they think you're talking to them in Chinese!
 
  #110  
Old 08-05-2014, 04:59 PM
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Well.......

Here we go. The crusade begins.

Now my car has been hesitating violently enough that I thought I end up on the side of the road stranded. Long story short, I took my car to the Ocala dealership. I didn't buy the car from them. I bought mine from the Orlando dealership. Ocala is 10 miles or so closer, and I bought my M3 from them. They convinced me to bring the car up there, so (against my better judgement) I took it there. I feel like I don't have a leg to stand on with them as I purchased the car elsewhere. They had an earlier appointment available, and I didn't want to have to have the car towed.

Anyway, the result was the same as what all of you had experienced.

The result,

"Checked faults and created log. There are no faults stored in vehicle at this time. Verified oil level and quality by removing oil filter and inspecting. Oil level shows full. Oil quality appears to be ok. No debris found in oil at this time. Checked transmission oil level and quality. Oil level is full. Quality appears ok at this time. Performed DME software update per WE30. Performed multiple test drives. Vibration may have improved some, but can be felt in all driving modes. Please advise customer: Due to subtlety of vibration, miles on vehicle, lack of codes stored, etc.; vibration could not be pinpointed at this time. This could be normal vibration. No other X51 package vehicles on the lot. Please request customer to monitor vibration for any change or frequency of occurrence."

My fear is that I know I can't live with this hesitation, and I will not be able to sell the car like this. Anyone that gets behind the wheel is going to ask, "What is wrong with this thing." I guess per Porsche I'm supposed to say, "Nothing..."

I don't know how you guys have lived with this issue. I've pinpointed it to 2,500-4,000 RPMs in any gear and any mode. It's early in the game, but I'm guessing I just keep going back to the dealer and then hire an attorney. I won't be able to sell the car and can't live with this issue.

I called Orlando and luckily they didn't cancel my Thursday appointment.

I can't believe this is happening!
Matt
 

Last edited by Money2536; 08-05-2014 at 05:04 PM.
  #111  
Old 08-05-2014, 05:05 PM
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Originally Posted by STG958 View Post
They think I'm nuts too. I repeat it like 5 times. Just bought my preowned 991 and they had fine nothing but wash it. They don't "detail" it until it sells. I told them not to touch it. They delivered it to me untouched, and didn't even take the window stickers off! Thank goodness!

Not surprising about the Turbo S. You talk to them about swirling and paint correction and they think you're talking to them in Chinese!
Yep, Chinese. My friend was looking at buying a used 335i from the same dealership. He was asking my advice. I asked him how the paint looked. He said it was flawless, but asked me to take a look at since I was going to be there today.

Swirl city...
 
  #112  
Old 08-05-2014, 06:32 PM
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"Vibration". I'm sure that's exactly what the service adviser was instructed to diagnose by you - a vibration. Oh the pitfalls of a limited vocabulary.

We all know that it feels like the most subtle of misfires. A slight shudder as you pass through the dead spot - as if you're lifting off the accelerator for a split second, just enough to lurch forward.

One a few occasions I just happened to pause at the perfect spot during acceleration, which resulted in the car bucking like crazy.

I quote a member on another forum "The other day I happened to blip my cruise control to exactly that spot and it was a strange sensation. I was worried that I was about to be swallowed up in some sort of vortex, so I blipped it up another 50 rpm or so."

A glimmer of hope is that this problem does not occur in all 991s and seems to be somewhat random, albeit without error codes. That would suggest that it's NOT normal and a fix to replicate the non-stumbling cars is possible.

If our problem suddenly appeared after xxx miles, could it be a flakey throttle position sensor?
Some have had crank sensor spacers installed, while others have suggested an issue with the OEM plenum flap.

I would be the first in line for a tune or a plenum were it not for my warranty being voided.

By the way, Porsche is well aware of this "normal" behavior...
 
  #113  
Old 08-05-2014, 06:49 PM
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Originally Posted by dux View Post
"Vibration". I'm sure that's exactly what the service adviser was instructed to diagnose by you - a vibration. Oh the pitfalls of a limited vocabulary.

We all know that it feels like the most subtle of misfires. A slight shudder as you pass through the dead spot - as if you're lifting off the accelerator for a split second, just enough to lurch forward.

One a few occasions I just happened to pause at the perfect spot during acceleration, which resulted in the car bucking like crazy.

I quote a member on another forum "The other day I happened to blip my cruise control to exactly that spot and it was a strange sensation. I was worried that I was about to be swallowed up in some sort of vortex, so I blipped it up another 50 rpm or so."

A glimmer of hope is that this problem does not occur in all 991s and seems to be somewhat random, albeit without error codes. That would suggest that it's NOT normal and a fix to replicate the non-stumbling cars is possible.

If our problem suddenly appeared after xxx miles, could it be a flakey throttle position sensor?
Some have had crank sensor spacers installed, while others have suggested an issue with the OEM plenum flap.

I would be the first in line for a tune or a plenum were it not for my warranty being voided.

By the way, Porsche is well aware of this "normal" behavior...
I'm going to be sure to have my dealership add the appropriate language to the next work order. Your description is perfect. I'm going to print this thread and others from Rennlist to take with me on Thursday.
 
  #114  
Old 08-05-2014, 06:55 PM
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I assume a lot of these service advisors and techs are totally clueless on how to diagnose problems without the computer giving them some sort of error message?

Like they need to be told what the problem is versus being very knowledgeable to be able to self diagnose it?
 
  #115  
Old 08-05-2014, 07:01 PM
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By the way folks, my galloping vehicle resorts to a mere canter with the A/C turned off.

So less load on the engine seems to make the stumble less noticeable.

Please try it and let me know if you have the same results.
 
  #116  
Old 08-05-2014, 07:11 PM
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Originally Posted by dux View Post
By the way folks, my galloping vehicle resorts to a mere canter with the A/C turned off.

So less load on the engine seems to make the stumble less noticeable.

Please try it and let me know if you have the same results.
I'll test that out tomorrow.
 
  #117  
Old 08-05-2014, 07:25 PM
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Mine gets particularly bad on a long incline such as a long on-ramp or a hill on an interstate, when I maintain the infamous 2500-2900 RPMs.
 

Last edited by mtony; 08-07-2014 at 06:27 AM.
  #118  
Old 08-05-2014, 10:55 PM
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My money's still on the Variocam system as the culprit. After reading through this description of how the system operates, I'm amazed it operates at all, let alone without the dreaded stumble.

https://dl.dropboxusercontent.com/u/...cam%20plus.pdf

A bazillion events (give or take a few million) must happen flawlessly in the blink of an eye for the system to operate seamlessly. As a WAG, I would guess that any hiccups in the system are related to oil and oil pressure, as hydraulics are responsible for much of the system's operation.

My biggest gripe is the fact that a less than seamless cam changeover apparently doesn't throw a code.
 
  #119  
Old 08-06-2014, 05:49 AM
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Originally Posted by mtony View Post
I was basically told that they all do that...
Originally Posted by stealthboy View Post
... said it was "normal behavior"
Originally Posted by Money2536 View Post
This is the first time in my life that I wished something would just break.
Not to defend Porsche here - because there does seem to be an issue - but it's gotta be tough for a technician to diagnose something like this, and even more so when several cars exhibit the exact same issue. I've gone through things like this with BMW, and it can be frustrating. Hopefully when enough people have complained something will be done. I know there's at least one other thread on Rennlist about this issue.

As for Mr. 2536 (Matt), I'm reminded of my last M5. It had some drivability issues, and I was never so happy as when that stupid check engine light finally came on. Now we can diagnose it!

Anyway, this really sucks for you guys that are having severe drivability issues, and I wish you all the best. I've gone through a few lemon issues (with BMW) and it seems to me that having strong documentation where the technician acknowledges the issue (rather than writing "customer claims..." they write "... problem still exists") is a big help when escalating through the bureaucracy.
 
  #120  
Old 08-06-2014, 06:23 AM
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I would think it would be easier to diagnose with several cars having the issue rather than one isolated incident. These techs see these cars everyday and I'm sure there are known problems that aren't big enough to have Porsche take action on until it spreads further or becomes a bigger issue. You really think somewhere down the line they're not aware of what the problem is??? Acknowledging it is another story ..
 

Last edited by STG991; 08-06-2014 at 06:25 AM.

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