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Discussion Starter #1 (Edited)
I've searched and havn't heard anyone talk about this so I'm guessing it might be something.

Last night on my way to the gym I decided to take the BS out. Mostly warmed up I had to merge into traffic on my street and that required most of the pedal. I had it in Sport with the PSE on. It was at about 160 degree engine temp. It reved out fine (but required backing off the pedal a bit, more on that in a min) then hit the 1/2 shift and "farted" Flopped down from 6000rpm to about 2500 for about a second, I backed off the pedal a bit more and up she came and away she went. The farting was the sound of the PSE closing, then opening again.

After my 500 mile trip back from ABQ to PHX I got gas at a Valerao, since then I have had a bit of a stumble, or miss. Sometimes its there some times not. If I come on the brakes hard coming up to a light it's there. Almost as if something moved, or came loose. If I roll up 'slow' it'll almost purr perfectly.

Second part of this is I thought it was the gas, had topped up a Costco, missing got a bit worse. I then noticed in Sport mode I could put my foot all the way down and it was like the car lost power. Back off the pedal a bit and bang, up she came and on came the power I expected at full peddle. I've had this before in Turbo and SC'd cars, as running lean, close the maf a touch and the air is choked to a point that it's then within range. I've noticed this more and more lately. I do not remember this on the drive home, last week.

Ok so the 3rd part of this is the PSE was installed just 2 weeks before I picked up the car. There are vacuum lines to the PSE. I can almost swear the PSE is 'on' in the range it used to muffle out. SO I think I have a vacuum leak to the exhaust. It's probably causing the missing and the pedal problem. I'm not sure if it could cause the flop out of the PDK unless the engine kicked in a limiter of some sort. The PSM had kicked in for a second before the shift, so I'm thinking the whole thing might be related.

I am probably going to try to get to the engine today and tap in my PSE over ride, and attempt to hunt the vacuum lines to the PSE.

Can you drive with the engine cover off and the top down? Or should I button the whole thing up before attempting a shakedown drive.
 

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Discussion Starter #2
Well I was right, there is a leak somewhere. I thought it was this: (I cut out the mangled part and put it back on, there was very little change)


BTW the solenoid for the 987.2 PSE is NOT in the middle of the engine bay, it's on the side.


Note the clear tubing is what the dealer put in for the PSE. Down around the pipes it changes to stainless braided. I tapped in a switch to bypass the PSE cut out.

I started the car with the engine cover off and when I tap the gas there is a high pitched sucking sound then the engine revs. I'm not sure if this is the drive by wire sound, and if it's normal or not. I'm waiting for the video to transcode now. There is also a vacuum line that goes through a pair of valves, I'm guessing the vario-ram. That could be the sound of the vario-ram I'm hearing.
 

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Discussion Starter #3 (Edited)
Only thing I can find is this guys video on youtube. It sounds just about like my 'fiiifft' when you crack the throttle open off idle.
 

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az erik,
You might want to check the vacuum hoses and hoses to air oil separator to see if you have a loose one. There are also hoses and actuators on the bottom of the plenum that could be the issue. It is more exciting but possibly more accurate to do this with the engine running. Good luck

Rob
 

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Discussion Starter #5
I was tying, but the drive by wire makes it really hard to be at the engine and the pedal. It's possible something under the plenum, I don't get the sound unless I get on the gas and even then it's for a split second then gone. Almost like a valve for the intake. Not sure, it's all buttoned up now, maybe drive it later. When if fell on the 1/2 shift it might have been PSM, though I didn't see a light at that time for it, but just before the shift.
 

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The symptoms seem to point to the intake flapper not activating. It is vacuum activated so if the diaphragm has a tear in it you would only hear it when the ECU was commanding the valve to open as you pass thru the opening point RPM. You could try working the throttle with a pole while you are at the engine bay to listen for a vacuum leak at the actuator.
 

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The sound is normal I just had my CS engine cover off the other day and was getting that relief / vacuum sound when blipping the throttle.
 

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Discussion Starter #8
There is a black vacuum line running right through the intake flap levers. I couldn't figure
Out a way to move it but both levers work if I push them. I'm looking for a 987.2 plenum diagram now as I think that's no a good idea, I couldn't get a picture of it, simply no room to. I haven't driven it yet. The ripped/cut hose didn't appear to go all the way through. It might have leaked a little. The video was taken after I had fixed that hose.


Sent from my iPhone using Tapatalk
 

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Discussion Starter #9
This is still happening and kind of getting worse, but only noticeable when not in sport or sport plus, and more noticeable when not up to temp.. I have a hesitation about 1/3rd throttle if driving normally. If I time it right the PDK shifts right when that kicks in. But if I put it in Sport it's not noticeable. My thought being the TB opens faster skipping the possibly sticky spot in the TB flap. Interestingly when turning on Sport my Sport exhaust gets louder as well, even though I have it over ridden by a switch. Like the TB cracks open a bit more, or possibly the plenum changing flow? Does anyone have a pointer as to what really happens when Sport is activated?

I feel kind of stupid as I'd been in the engine bay when I posted this, I had tried to figure out a way to get the TB off, but didn't think about pulling the plenum in order to, now that I found an article on it I'll pull and clean it, got a new filter to drop in as well.
 

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I'm thinking its the flap on the intake distributor. How's the RPM on idle?
 

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It sounds like a vacuum problem with the PDK there is a special installation note for PDK cars when installing PSE systems. If you don't have those instructions pm me and I will email the PSE pdf instructions to you.

Cman21
 

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Discussion Starter #12
It sounds like a vacuum problem with the PDK there is a special installation note for PDK cars when installing PSE systems. If you don't have those instructions pm me and I will email the PSE pdf instructions to you.

Cman21
Yeah I don't have that as the PSE was istalled bt the ABQ Porsche dealer. I have put in a switched cut out for the vacuum solenoid that runs the PSE.

I'm thinking its the flap on the intake distributor. How's the RPM on idle?
Idle is pretty smooth, there is an occasional feel of a miss but not rough or odd. I havn't driven it in about 3 weeks and am planning to tomorrow. Might pull the engine bay cover before going for a drive. I've felt lean/rich run conditions in some of my other cars but this doesn't feel like that, more the blade speed for the TB not being smooth. I'm hoping to pull it and clean it at some point. I didn't realize I'd have to pull the plenum to do so.
 

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Discussion Starter #13
Took it out and it drove pretty much the same. I did notice that there almost sounds like the PSE flaps activating on up shifts, the shift sounds more like a fart than a shift. Kind of Fsssst when shifting. I didn't get a chance to pull the plenum yet, but will soon as I got a 15 day maint reminder.
 
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