Switchfoot614

Threw a code. GTS was a MT and was severely overrevved long before I owned it. Porsche dealer PPI didnt even think to check for DME reports on a cayenne. I purchased from an indy shop. Long story short, stretched timing chain, collapsed chain tensioner, bad solenoids and a few bad variable lift followers. Gulp, she did run like a scalded cat after I was done though.

NiteJav

On my 991 I ran into this issue.... https://rennlist.com/forums/991/8307...l#post14251115

FireHouse1

I have a 2009 c4s and am experiencing the same sound and slight hesitation. Engine load does make a difference. Wish there was a fix out there because I find it annoying more than anything. Where do the tuners weigh in on this? Sharkwerks guys? Fabspeed guys??

Bruce In Philly

Honestly, I just gave up. I still find it annoying... less so now that I know it is not a failing component. I was going to replace the actuators at my next plug change in 5K miles but I am just giving up. I still might do it ..... but from what I read, if these actuators are not working correctly, they will throw a code... or a code of some sort is thrown.

If the load is just right.... on an incline.... the miss can really jerk the car.

I dunno....

Peace
Bruce In Philly

Bruce In Philly

Bump....

I have 118K on my 2009 C2S and am about to place an order for plugs et al for my 120K maintenance .... so, do I order the actuators for a total of $300 ?????

PS: I never collected Durametric live values because I just don;t know what to look for. I suppose I could but again, just not sure what to look for.

Any more data about these things?

Peace
Bruce in Philly

ChicagoSpeed996

Bruce, I was the one that came up with the solution to a symptom that exhibits itself as a 2500 rpm hesitation, seems like the engine almost misfire, or coughed, then it continues through the rpm. No codes. If this sounds like you, try replacing your O2 sensors. I did and the hesitation has been gone for over 1000 miles. Worth a shot since you are considering throwing some parts at the problem. They are about $120 a piece (replace both.).

Bruce In Philly

Interesting...... did you have this problem for all of your ownership or did it progressively change. Mine has been this way for the life of my ownership, about 100K of driving. I thought and O2 sensor would change progressively no?

Peace
Bruce in Philly

tuxkilla

Bruce you should change the actuators and the O2 sensors and if it fixes the hesitation, I will name my first born son after you.


Thanks
Rob

lowbee

deleted

Petza914

I don't know what the .2 airbox looks like, but in the .1 it had this extra leg off the intake hose that went to a flap in the box called a Helmholz resonator or something like that. Most of the tuners sold a kit to cap this off (I believe a certain brand of oil bottle cap was exactly the right size too), but they said that taking that secondary air path with a flap in it out of the equation improved response. You'll also notice that none of the aftermarket air intakes preserve this functionality. I'm wondering if anyone else with a 2009 had this issue, replaced their intake, and noticed the hesitation was gone? Alternatively, you could try blocking off this part of the intake tract if the .2 does have such a thing.

Bruce In Philly

You may be on to something....... this flap is in the S models and not the base... so this weekend, I plan on disconnecting that vacuum thingy located on the right side of the airbox. Maybe just unplug the electrical line as the air line is on really tight.

Then I will drive it to see what effect if any this has. I am not optimistic as those with base models experience the same hesitation.... but I will try.. easy test and I have a Durametric to reset any codes tripped.

Peace
Bruce in Philly

Bruce In Philly

Part of me really wants to do this but now we are talking about what, $600 in parts for an experiment? I dunno........ hmmmmm......

I feel the same as you.... this hesitation really pisses me off. It is not subtle if conditions are right..... such as mild acceleration up an incline.

I am a bit suspicious that the problem is caused by the O2 sensors..... as their performance can change over time until they go out of range and trip a dash light (first occasionally, then solid.... showing they deteriorate). In other words, if it were the O2 sensors, then the hesitation would have changed over the 100K miles I drove the car and it has not No?... been pretty darn consistent.

Maybe though, who the heck knows. Maybe the sensors were a bit out of spec from the factory and sends incorrect information to the computer.

So Rob, what are you going to do about yours?

Peace
Bruce in Philly

Petza914

Not knowing what it looks like exactly, I can't advise on the best way to bypass it for your test, but it's possible the flap is on a spring and that once airflow reaches a certain amount or velocity that it mechanically moves the flap so just doing an electrical connection may not negate it. Also, look at wherever that vacuum line you're talking about unplugging ties in upstream - if it will allow for unmetered air to enter through that line on the downstream side of the MAF, that will create a different problem. That's why the blockoff kits for the .1 cover the hole inside the tube, but leave the tubes connected.


Silver cap is blocking airflow through the helmholz resonator



See the indentation in the first photo and orient the airbox the same way visually and you'll see what's under that opening (this little compartment)



See two intake pipes merging together prior to the throttle body



What's interesting about this is that the intake path from the resonator actually ties in downstream of the MAF - how does that work?

tuxkilla

I'm not sure what do to either. I had an e30 at one time that had an 02 sensor go out that caused a bucking condition without a check engine light, but it wasn't nearly as abrupt as the hesitation I am seeing with the 997.2. The accompanying change in noise (I also have a center bypass and can hear what you are hearing as the hesitation occurs) makes me think its more towards the actuators, as an intake flap wouldn't be so abrupt IMO. I suspect its something in the way the ECU is handling certain parameters, and unless someone can fix that portion of the code, its going to continue to happen. I have an EVOMS tune on my car and the hesitation is still there FWIW.

__ Charley __

Hi Guys!

Here is my experience. I had the hesitation and stumble problem. 991.1 4s. Stumble at around 2500 rpm even on the cruse control. On our cars there are 4 solenoid. 2 for the cams and 2 for the valves. I changed 1 cam and 1 valve cylinder 4-5-6. PROBLEM FIXED!! Have these solenoid checked I'm sure that's the answer to the stumble and hesitation!
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