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Car sometimes jerks as I’m coming to a stop - am I being paranoid


Haynnes08

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Hi all,

Newbie to BoXa.net and to the Porsche world. 
About 6 weeks ago I bought a 987 gen 2 (2011) 2.9 PDK, loving it so far but in the last two days I’ve noticed two things.

Firstly when I reverse out of the drive in the morning and put car in drive it feel slow to engage the gear to go forward. Does not happen until the next day.

Secondly sometimes when I slow down for traffic lights it seems to jerk a little.

According to the service history and receipt the transmission fluid was changed by OPC two years ago.

Any ideas or advice would be highly appreciated.

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welcome 


Sounds normal to me. 

Gearbox definitely gets cold and engaging forward or reverse first thing can sometimes feel odd.
 

regarding the fluid change (and you may already know this so apologies if I am teaching you to suck eggs ) but there are two sets of fluids in the pdk   Clutch and Gearbox   On the 987 the clutch fluid change interval is 6 yrs/60k miles   The gearbox oil is 12yrs /120k Miles. If yours was serviced at OPC then probably safe to assume that it was (correctly) the clutch fluid change   But I have read of some Indy’s changing the gearbox oil not the clutch fluid  

the 981 and later skip the 6yr clutch fluid change and have it all done in one hit at 12yr  

jerking when coming to a stop (always seems to be roundabouts). Yup.  But that does improve with “technique”. I found it much less pronounced once I got used to the shift points and learned to lift of the brake slightly as it shifted down. It’s very subtle but in my case it made a difference.  Also. I find the pdk box is better at predicting gears for junctions and roundabouts if I brake slightly harder to start with then ease off rather then my usual manual style of gentle braking and then either lift off brake and accelerating or braking harder if I need to stop.  Easier to do than to write and its a subtle variation.  

I previously had a 987 2.9 PDK and now a 987 3.4 PDK. The jerkiness was more pronounced in the 2.9, I put that down the the 3.4 having more torque and the gearbox have a “wider choice” of gears/revs. I had the clutch fluid changed and it made it a little better (perhaps psychologically). 

there is also a “torque slip pdk recalibration” procedure which is part of the “so you have removed/ replaced  your battery “ procedure that’s a bit black magic and involves idling with the lights and aircon off in gear with you foot on the brake and then turning on lights and a/c. I can dig out the procedure if you want it. I did it on my 2.9 and again I don’t think it made much a huge difference.  

we like pictures and details and specs of newly acquired cars on here so figure out how to post pictures and show off your new toy.  

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56 minutes ago, Paul P said:

there is also a “torque slip pdk recalibration” procedure which is part of the “so you have removed/ replaced  your battery “ procedure that’s a bit black magic and involves idling with the lights and aircon off in gear with you foot on the brake and then turning on lights and a/c.

Gosh - I don't have a PDK car but that sounds utterly nuts! 

Yes, please do post the details! I never cease to be amazed at the amount of electronic resetting and recalibration necessary on these cars. :)

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Thanks Paul P. If you can send me the step for the "torque slip pdk recalibration” that would be highly appreciated.

Hopefully the car is getting a full detail on the 18th March and then I have decals going on. Once those are done I will definitely post pics.

Again thanks in advance.

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27 minutes ago, zcacogp said:

Gosh - I don't have a PDK car but that sounds utterly nuts! 

Yes, please do post the details! I never cease to be amazed at the amount of electronic resetting and recalibration necessary on these cars. :)

I will dig the details out.  In typical Porsche style there’s a very detailed list of instructions that are probably largely irrelevant 99% of the time. 
 

but it’s not just Porsche. I have a 17 year old Toyota as a daily driver.  That has a menu option on the sat nav to tell it to recalibrate when you put new tyres on the car or disconnect the battery so it can guesstimate distance travelled if it loses gps lock. 

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Here's what I have - having re-read it it doesn't specifically say "when you have disconnected the battery" - but it does talk about "when adaptions have been lost" and in other reading "adaptions are lost when disconnecting the battery " - as I say - all black magic and likely completely pointless - but I did it on mine when I had the steering wheel off and the battery disconnected - i would say it made no difference.

Torque loss
Only necessary for vehicles with PDK
How?

Information

1. Engine idling:
1.1. Meet preconditions:
1.1.1. Engine at operating temperature.
1.2. Engine idling for 3 minutes without activating loads.
1.3. Engine idling for 3 minutes with air conditioning on.
1.4. Engine idling for 3 minutes with air conditioning on and transmission range engaged.

I have seen this sequence (or variations of it) listed for "PDK reset" 

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On my PDK it is possible to make it snatch at very low speeds. Rather as you could do with a manual too, with the clutch fully home and very low engine revs. But careful throttle control minimises this. At very slow speeds and parking etc, they do behave a bit differently to a 'normal' auto. But a small price to pay for a generally superb transmission.

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3 minutes ago, Haynnes08 said:

Thanks @DaveEFI perhaps unknowingly I'm being aggressive. 

I agree with Dave. There's a few tweaks to your driving style that will start to come more naturally,  I find it still happens to me - often when I am slowing with the expectation of a stop ,need to slow to let someone through a gap and then they stop and flash you through - when you reapply the throttle the car snatches - i think sometimes it's maybe already changed down (ahead of the "deployment") and suddenly cant work out if it should take the lower or the current gear.

super slow stop/start traffic isn't the PDK's strong point for sure.

 

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Hi all, after purchasing my 2.9 Gen 2 I carried out this procedure to delete all the stored information, it has to learn its way again and then adapts to your driving conditions and style, it worked for me and smoothed the box and changes. The first part is from Porsche and the quick access is from another source, cant remember where I found it but would have ben a reputable source.

  My car has covered less than 23k miles and I presumed it had spent time moving slowly in traffic....The quick access is what worked best for me.

 

PDK Reset

Necessary after:

Re-Programming DME control unit (Digital Motor Electronics)

Replacing DME unit.

                Re-programming PDK control unit.

 

Necessary before:

                Re-calibrating PDK

 

Information

                The accelerator pedal must always be pressed after approx. 1.5 mins (1min 30 secs) since each adaption step is limited to 5Nm.

 

How

 

1.       Engine idling

1.1   Meet preconditions

1.1.1         Engine at operating temperature

1.2   Engine idle for 3 mins without activating loads aircon radio etc off, press accelerator pedal once after approx. 1.5mins during this time

1.3   Engine idle for another 3 mins with aircon on, press accelerator pedal once after approx. 1.5mins during this time

1.4   Engine idling for another 3 mins with aircon on and transmission range engaged, press accelerator pedal once after approx. 1.5mins during this time

 

Place in park and switch engine off, lock car and leave for 1 minute. PDK is reset.

Unlock and start the car. Drive to start learning your PDK

 

If the purge fan is running then the programme will not be complete until stopped. This will be 1 minute after purge fan stops running.

 

Quick access process

 

1.       Engine hot turn off AC radio etc.

2.       Stop engine

3.       Restart engine and run for 3 mins blipping the throttle at 1min 30 secs

4.       Turn on AC and run for another 3 mins blipping throttle at 1min 30 secs

5.        Put in drive and run for another 3 mins blipping throttle at 1min 30 secs (place foot on brake during blipping)

6.       Put in park, turn off engine, remove key and yourself, lock and leave car for 1 minute.

7.       Go for drive to restart the learning of the PDK.

 

Timings review

Time                                                                      Job

0 mins                                                   Start (no AC)

1 mins 30 secs                                   Blip throttle once

3 mins                                                   Turn on AC

4 mins 30 secs                                   Blip throttle

6 mins                                                   put in Drive (left foot on brake)

7 mins 30 secs                                   Blip throttle

9 mins                                                   put in park and switch off, leave car and lock for 1 minute

 

Go for a drive and enjoy relearning PDK.

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I have read the quick access one somewhere as well - like you can't remember / find the source - your one also has the blip mentioned - again -I have seen that in a Porsche bulletin but I couldn't find it.

 I think this is the more definitive version of the " black magic" .

 

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I'll give an example of where moving slowly can be more difficult than a 'normal' auto. A car park I use has the roads normal tarmac, but the parking bays just compacted earth. So a lip between them. If backing out, and wanting to so so slowly due to the poor rear visibility with the hood up, and lots of people and dogs etc around, it can be tricky to get over that lip without lurching. On my other car with a normal auto, I'd simply increase the revs slightly, and control the movement using the footbrake, and my left foot. Try the same on the PDK, and the clutch disengages.

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