981 PDK hesitation/shunt

981 PDK hesitation/shunt

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Mario149

Original Poster:

7,750 posts

177 months

Friday 10th March 2017
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I'm pretty sure I'm not imagining it - I'm convinced that when I'm in a high gear (say 4th or above, may happen lower but it's difficult to tell) at medium revs (say 3k or so) if I'm cruising and suddenly plant my foot (in manual mode or without the car changing gear) there seems to be a hesitation/shunting/bumping for a sec or so before the car accelerates cleanly. At first I thought it was just the little bumps in the road you feel fooling me as I was obsessing - it's that mild, difficult to tell whether it's vertical or longitudinal - but the "bumps" always seem to happen more for the first second or so when accelerating as described.

Anyone else had this problem? Either feels like the engine is hesitating or that the PDK clutch is slipping...or that I'm going nuts.

Car is booked to go for its first service in July, so trying to work out whether to wait until then to get it looked at, or take it in before. Feel quite bad about doing the latter as it's already been in twice for warranty stuff and one of those was me being an idiot :/


Maxym

2,018 posts

235 months

Saturday 11th March 2017
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Not had anything like that.

bcr5784

7,102 posts

144 months

Saturday 11th March 2017
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Someone on here posted that they had had their dynamic engine mounts replaced 3 times. Could it be that?

7184c

415 posts

90 months

Saturday 11th March 2017
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Not experienced anything like that. Does it happen in all situations i.e. Normal/Sport/Sport plus if applicable?

anonymous-user

53 months

Saturday 11th March 2017
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Mario149 said:
in a high gear at medium revs (say 3k or so) if I'm cruising and suddenly plant my foot (in manual mode or without the car changing gear) there seems to be a hesitation/shunting/bumping for a sec or so before the car accelerates cleanly.
It's sudden high torque bouncing the springs in the clutches and you can get the same effect in a manual car. If you leave the PDK in auto it will engage the right gear and this won't happen.

The only place I've ever noticed a difference between PDK and a torque converter auto is crawling in traffic, where occasionally there will be a slight jerk as clutches engage/disengage.

The classic way to test a manual car for a worn clutch is to drive exactly in the way you have described; plant foot at medium rpm in high gear. The high torque will cause a worn clutch to slip.

ellesmereFNC

131 posts

215 months

Saturday 11th March 2017
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We have the same problem on our GTS, its going into the dealer on Monday to look at this and a couple of other bits. Feels a bit like a fuelling issue as I initially thought it was the traction control kicking in.

JC360

36 posts

140 months

Saturday 11th March 2017
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Is it not transmission shunt?

Drove a few Porsches and no matter how carefully you apply the throttle there is evident shunting of the gearbox and transmission, especially on the motorway.

Mario149

Original Poster:

7,750 posts

177 months

Saturday 11th March 2017
quotequote all
ellesmereFNC said:
We have the same problem on our GTS, its going into the dealer on Monday to look at this and a couple of other bits. Feels a bit like a fuelling issue as I initially thought it was the traction control kicking in.
Thanks for the comments so far. To be honest if if had to put money on it I'd say it was engine rather than transmission related, maybe fuelling as suggested above^^. Like I said, feels like hesitation. I've driven cars where there's drivetrain shunt and the slack is taken up only once I.e. one bump rather than a series of them.

Green1man

549 posts

87 months

Saturday 11th March 2017
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This to me sounds like you are confusing the PDK gearbox. Say you are in 4th it thinks you are going to change to 5th next, but you plant the throttle, the car needs to change down but you have 5th selected at the 2nd clutch, so has to swap that out and put third in, at the same time the engine is trying to deliver more torque and revs. Hence you get a jerk/shunt. PDKs
Get it right 90% of the time but not always.

Sorry just reread your post, it seems you are in manual mode, so cannot be this- not sure then.

bcr5784

7,102 posts

144 months

Sunday 12th March 2017
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JC360 said:
Is it not transmission shunt?

Drove a few Porsches and no matter how carefully you apply the throttle there is evident shunting of the gearbox and transmission, especially on the motorway.
Certainly not true of mine - but it hasn't got Chronosport and the dynamic engine mounts that go with it. I still wonder if that is a factor.

ellesmereFNC

131 posts

215 months

Monday 13th March 2017
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Just dropped the CGTS off at the local OPC, went out with the technician and the initial thoughts are either a failing coil pack or a sticking / failing valve train solenoid...

Guess i'll know later on, also this happens in auto or manual and makes no difference if its in standard, sport or sport +


Mario149

Original Poster:

7,750 posts

177 months

Monday 13th March 2017
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ellesmereFNC said:
Just dropped the CGTS off at the local OPC, went out with the technician and the initial thoughts are either a failing coil pack or a sticking / failing valve train solenoid...

Guess i'll know later on, also this happens in auto or manual and makes no difference if its in standard, sport or sport +
Good to know, I may try and get mine in then before its service in July.

speedyman

1,523 posts

233 months

Monday 13th March 2017
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Had something like that on my boxster, bit like a misfire, eventually it triggered a cel light on the dash. Turned out to be a loose connection on one coil pack.

Mario149

Original Poster:

7,750 posts

177 months

Monday 13th March 2017
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Have bitten the bullet and booked mine in for Friday. They'll look at the exhaust tips as well while they're at it as they appear to have the par for the course corrosion on them.

ellesmereFNC

131 posts

215 months

Tuesday 14th March 2017
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Quick update...now looks like it might be the high pressure fuel pump.


ellesmereFNC

131 posts

215 months

Thursday 16th March 2017
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Well that didn't sort it...!

Technician can feel the problem but car has no fault codes, the search will continue.

Mario149

Original Poster:

7,750 posts

177 months

Thursday 16th March 2017
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ellesmereFNC said:
Well that didn't sort it...!

Technician can feel the problem but car has no fault codes, the search will continue.
Oh no! What a pain! The hesitation on my car now seems to be intermittent, could feel it yesterday but not the day before frown

ATM

18,092 posts

218 months

Thursday 16th March 2017
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I've noticed a small problem with mine. When I'm going slowly in say 3rd and I start to brake gently I feel a shove or shunt as it downshifts to say 2nd. These downshifts used to be smoother than a smooth thing. Now they are noticeable.

Mario149

Original Poster:

7,750 posts

177 months

Thursday 16th March 2017
quotequote all
ATM said:
I've noticed a small problem with mine. When I'm going slowly in say 3rd and I start to brake gently I feel a shove or shunt as it downshifts to say 2nd. These downshifts used to be smoother than a smooth thing. Now they are noticeable.
Funny you should mention it, but I was also thinking that some of the gear shifts weren't as smooth as they used be.

ATM

18,092 posts

218 months

Thursday 16th March 2017
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Mario149 said:
ATM said:
I've noticed a small problem with mine. When I'm going slowly in say 3rd and I start to brake gently I feel a shove or shunt as it downshifts to say 2nd. These downshifts used to be smoother than a smooth thing. Now they are noticeable.
Funny you should mention it, but I was also thinking that some of the gear shifts weren't as smooth as they used be.
Right

If I bought the car today I would not think anything of it. But I have experienced better 12 months ago. Is there any adjustment for the clutch [as it ages] or is this all automatic / computer controlled.