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Engine stumble/hesitation around 2500 RPM?

 
  #46  
Old 07-26-2013, 07:10 AM
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Isn't it a characteristic (albeit an annoying one) of the variocam in which case not likely to be fixable.
 
  #47  
Old 07-26-2013, 08:05 AM
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The Ss do have variable intake geometry which may be malfunctioning. I'd definitely have the dealer put it on the scope.

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  #48  
Old 07-26-2013, 03:16 PM
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Base built 4/12 with chrono package. Glad to report silky smooth all the way in either auto or manual in normal, sport, and sport plus. No hesitation of any kind.
 
  #49  
Old 07-26-2013, 06:05 PM
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the last PDK update I had a month ago from dealer resolved that issue for me. don't even bother asking me how or why
 
  #50  
Old 07-26-2013, 06:29 PM
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Originally Posted by trysixty View Post
the last PDK update I had a month ago from dealer resolved that issue for me. don't even bother asking me how or why
I had a PDK "update" a month ago and it did nothing to improve this issue. Are you saying that you had this issue and now it's gone? Please provide some more information!
 
  #51  
Old 07-26-2013, 06:55 PM
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Originally Posted by mtony View Post
I had a PDK "update" a month ago and it did nothing to improve this issue. Are you saying that you had this issue and now it's gone? Please provide some more information!
Like I said in post not sure why. It was the may update that was released about 3 weeks after the April update. Again I don't know why or how but it is gone
 
  #52  
Old 10-22-2013, 02:52 PM
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Hey folks.
Just checking in to see if anyone has found a definitive solution to this extremely annoying problem.

Thx
 
  #53  
Old 10-22-2013, 03:23 PM
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I have almost 8k mi on my 2013 C4S with PDK, and I have not observed any hesitation with any gear at any rpm. Doesn't sound like it's a normal PDK behavior. Hope there is a solution for it; sounds annoying.
 
  #54  
Old 10-23-2013, 01:23 PM
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Originally Posted by mtony View Post
Mine does it warm or cold. Felt mostly in 2nd and 3rd gears but I can get it to do it in any gear if I accelerate briskly from very low RPMs (not quite lugging the engine, but close).
+1
Mine is a '12 997.2 C4S.

I only use Shell 93.

I drive the car really hard all the time to avoid it, but sometimes it happens. It really detracts from my enjoyment of the car.

I suspect that most 997s and 991s do it. Those owners that testified to not having this problem, might be driving the car in auto (without activating the "sport" function) so the car hardly ever reaches 3k rpm. Just my .2
 
  #55  
Old 10-23-2013, 01:43 PM
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"The hesitation I was experiencing when opening the throttle at around 2000rpm seems to have been down to lambda sensors. It took a local Porsche specialist with 20 years Porsche motorsport experience and a full factory PIWIS (with full Porsche Technical backup) the best part of 2 hours to find what was happening. No fault codes, just an aged and slightly out-of-calibration sensor.

Replacing both pre-cat lambdas solved the issue.

As an aside, I'm rapidly starting to learn that these cars don't throw fault codes until something very major is wrong. Sensors (especially MAF/Lambdas) can be far enough away from spec to have the car running like a dog, but without throwing a code. Cursory use of the PIWIS just to look for fault codes will not find the majority of issues that can cause the cars to run less then optimally. The PIWIS is capable of reading every conceivable operating parameter in real time, but without someone who REALLY understands engines (mechanically) and the DME systems (in real depth) to interpret what they're seeing, most faults will never be found"

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The post above was made in another thread by Ian_UK1 some years ago (his car is a '10 997.2 C2S). From what I understand in his post, the problem was solved by changing the pre-cat lambda sensors. My service tech would not even consider doing this to my car without a code.

Maybe somebody with a good relation with his service tech can have this done and report back?
 
  #56  
Old 10-23-2013, 02:26 PM
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Originally Posted by MMK110464 View Post
+1
Mine is a '12 997.2 C4S.

I only use Shell 93.

I drive the car really hard all the time to avoid it, but sometimes it happens. It really detracts from my enjoyment of the car.

I suspect that most 997s and 991s do it. Those owners that testified to not having this problem, might be driving the car in auto (without activating the "sport" function) so the car hardly ever reaches 3k rpm. Just my .2
I suspect that you are correct. If I drive my car in automatic, it is hard to reproduce the issue because it rarely reaches the RPMs in question. If I could make the car get to the RPMs in question, I would be too hard on the gas for the issue to occur.
 
  #57  
Old 10-23-2013, 02:29 PM
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I'd pay for the damn parts myself if that fixed the problem.

If you let the revs drop to 2k out of 1st gear and gradually accelerate in 2nd gear to ~3k rpm, you'd have to be in a coma not to feel the dead patch and subsequent jerk at 2500rpm.

Unfortunately we don't all want to drive really hard all the time to avoid this "characteristic" (especially with a cold engine or in school zones).
And because their flawed product doesn't throw a code we are forced to live with this "feature".

Porsche seem to have difficulty acknowledging obvious and wide scale issues such as stalling, engines dying and not restarting, design flaws in the C4S fuel tank, hesitation etc. But to tell your customer that the lack of an error code means that it's probably a feature, is asinine to say the least...
 
  #58  
Old 10-23-2013, 02:43 PM
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"Sorry sir but we're not seeing any fault codes, so everything must be fine.."

 
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  #59  
Old 10-23-2013, 06:25 PM
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Originally Posted by mtony View Post
I suspect that you are correct. If I drive my car in automatic, it is hard to reproduce the issue because it rarely reaches the RPMs in question. If I could make the car get to the RPMs in question, I would be too hard on the gas for the issue to occur.
I drive my car (C2) PDK in Sport and + all the time and have not had this problem.
I was thinking it was the variable intake in the S that was not working properly. Even the HP / Torque curves from working properly working engines are jerky and I'm sure if the servos are not working properly it would be even worse. Hopefully you guys can find a good dealer who can diagnose the problem. I sympathize with your problem; and if were happening to me, I would not put up with it. Hope you get if fixed.

ChuckJ
 
  #60  
Old 10-24-2013, 05:18 AM
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Using RON 91.5 (no ethanol mix) here.
Definitely no issue in any mode and any kind of driving from relaxed in normal mode to "hell is on fire" in Sport+.
No hesitation - just "go" from any RPM.

Rainier
 

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