Bruce In Philly

Interesting to see folks finding this thread....

Update since my August post... I stand by what I wrote in the original post above. It still has the thump, it is minor and was made more minor by the software update. Every once in a while, given a particular set of events I get a harder thump. Usually when I pull off the throttle, drift the RPMs down under 3K, then add some throttle when going up a hill (load).

I firmly believe it is the variocam actuator as that pin slams into place and the engine makes a hard transition to its new, high lift state.

What puzzles me, is why isn't everyone experiencing it? The design is the design is the design...

Peace
Bruce in Philly

slicky rick

Maybe everyone drives differently and maybe your driving style makes the thump come out.

kouzman

great info man. i have the same kind of transition at around 2700rpm... I will definitely let my dealer know when i take it for service.

wheeler

Well, I'm guessing the PDK cars are probably not even registering to their owners. I think it's accentuated by the manual shifting and down shifting and hitting that point with vastly different throttle speeds and clutch/shift scenarios. I seem to notice it more when the car is cool/cold, if I'm driving to warm the car up, slower, lingering around that rpm point longer, shifting slower, etc. and it's almost always in normal mode. Normal mode seems to be almost dumbed down TOO much...like Porsche was trying to put some WOW in the sport mode button. My F150 throttle reacts faster off dead idle than my 997...that's just messed up. It's a LOT better in sport mode. Now, the one thing I can see with Porsche's reasoning is the clutch and touchy throttle in sport mode is definitely not for novices. It took me quite a few hours to drive it smoothly and even more control to be able to leave it in sport mode for start and stop driving (now I almost always drive in sport). You know, if you don't get it just right or apply too much throttle, start engaging the clutch, back off, let clutch out it bucks like a horse. Not exactly the experience you want a test driving customer to have with their possible dream car. Still the dead response off dead idle is just weird and really screws with me in normal mode, when trying to drive mellow, in traffic.

Having spent hours and HOURS jetting 2 stroke and 4 stroke dirt bikes for woods and high alt riding, I am extremely particular and sensitive to throttle response and any glitches or weirdness in throttle transition. This is obviously NOT major issue, but it's certainly not perfect either. I think it's more a case of either the others not noticing it either don't care or don't identify it or have pdk.

Misdirection

Funny enough, I feel like it's much easier to be smooth on upshifts on a moderately spirited drive in sport mode, especially 1-2. Probably just my technique. Also, interestingly, I prefer the normal mode's throttle sensitivity when on the track (easier to be smooth on/off throttle), but you can't have the extra leniency of PSM in Sport mode with the normal throttle setting, sadly.

MMK110464

I have the exact same symptoms.
2012 C4S 997.2

There are many more drivers experiencing this; some have posted so in different threads here and on the other site.

In my opinion the vast majority of cars have this issue but it will only show under certain conditions. Regarding PDK, if you drive your car in auto normal, you will never feel it because the up shifts are made way before 3k rpm; if you drive auto sport you might be able to feel it but not always. However, if you drive manual and go easy on the throttle you will feel it every time it gets near 3k rpm.

People that drive MT cars have told me that they feel it all the time unless they are driving the car hard.

The only documented case of somebody fixing this problem is a post by a British owner who reported he changed the lambda sensors and it fixed the problem. I tried to contact him to no avail.

GSIRM3

I have a 2012 GTS with 6 speed and have never experienced this issue.

wheeler

Drove my car quite a bit yesterday, dry conditions, sunny, 30-32 degrees. Noticed the miss/hesitation more that ever. Seemed to be as low as 2500 rpm at times and never over 2800. Even my 15 yo son who doesn't drive the car (manual) looked over a couple of times and said "what was that??". The stumble has certainly gotten more pronounced, nothing subtle about it. Next trip to the dealer I'm driving the tech around. This "we were unable to reproduce the symptom" bull**** isn't going to play anymore. It's gotten to the point it's annoying and causes some rough shifts from 1st to 2nd. I agree with above, if you drive it in a more spirited manner the shifts are smoother, but trying to finesse it around in a less hoon-like manner produces the symptom. Someone mentioned the variable cam as being a possible culprit, this feels more like what it COULD be as it's certainly rpm/load related.

fskof

Bruce - Thanks for the write up

Wheeler - Keep us updated

USMC_DS1

Something that has worked well for me in these types of "we can't reproduce the symptom" situations. Offer to take the p-tech to lunch somewhere ~10-15mins drive away... have him drive the car while you point out the issue from the passenger seat. It's amazing what they discover when you're on friendly terms after a free lunch... GL.

tbrom

You mention below that the only reported fix was by some British guy that replaced his lamda sensors - what are the lamda sensors and has anyone mentioned this to the dealer? I would very much like to know what the dealers tech guy would have to say about this. Surely there is some mechanic in a Porsche dealer's shop that actually owns/drives a 997.2 that has experienced this that must have a solution or at least tried to find a solution. I am very curious about a "lamda sensor solution" - not that I don't believe it - I would just like to know more about it.

Especially since I am looking for a 2009 Targa 4 right now. I really don't want to get blind sided with an issue like this. This is the kind of thing that would bug me to death! Actually this is the kind of thing that may just make me not want to buy the car. I can't believe if this is a typical experience that this thread doesn't have a lot more chiming in - like the IMS issue thread. I mean just how "widespread" is this condition? Maybe a thread entitled "Lamda Sensors" would be a good thread to start - yes?

wheeler

Tbrom - I don't want to make it in any way shape or form like an IMS issue. My car is very bad *** and quite satisfying to drive. :-) However this little glitch seems like something that a car of this caliber should not have. It took me a while to even notice it as a new-to-me car. Maybe a little more than a nit pick, but hardly enough to call it quits!

MMK110464

Wheeler:


Please do report back after visiting the dealer.

Thanks,

Moises

MMK110464

(I also reported these findings in the 991 forum where they have a dedicated thread to this problem)

I have a 2012 997.2 C4S and it has been doing the stumbling/hesitation at around 3k rpm since I bought it.

The simple procedure outlined below has eliminated the problem for me almost completely.

As you all know, the car starts the auto idle procedure when its been parked for several hours (which is usually the case in the morning when the car is started for the first time that day) and the revs go to approximately 1,500 rpm for about 1 minute. When this happens, I immediately blip the gas and take the revs to between 3-4k rpm. This will deactivate the auto idle and the revs will fall to its normal level of 800-850.

Thats it. This procedure will keep your car stumble free as long as the auto idle is not allowed to engage.

Please give a try and give your feedback

beden1

Same here. I have not experienced this problem with my 2012 GTS.