981 PDK hesitation/shunt
Discussion
ATM said:
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. 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.
Two things,
1. Have you got the sport button pressed?
2. Have you been driving the car more enthusiastically?
IIRC the PDK transmission has several shift maps and it will switch between them either if it is told to or if it "learns" how the driver is driving. I think the transmission has more "maps" than there are switch positions. The maps control both when the transmission shifts and how firmly it shifts.
I have heard of cases where people take modern auto cars back to the dealer complaining that it's changing gear incorrectly. Dealer simply asks, "Has someone else been driving the car?". If the answer is "yes" then that's often the explanation; the car has simply learnt someone else's driving style. Eventually it will either default back to its normal mode or learn the style of the next driver.
Some extracts from a PDK driver's manual,
Select position D for "normal" driving.
The gears are shifted automatically according to the accelerator position and speed. Depending on the way the vehicle is driven (economical, comfortable or sporty driving style) and on the resistance (e.g. uphill), the gearchanging points are shifted towards higher or lower engine-speed ranges.
The accelerator position, driving speed, engine speed, longitudinal and lateral acceleration and the road profile all have an influence on the gearchanging characteristic.
When you brake, and depending on the amount of deceleration, the PDK transmission changes down earlier.
With a sporty driving style, downshifts are already initiated when the brake pedal is touched lightly. This further enhances a dynamic driving style.
The PDK transmission temporarily changes to the sportiest gear-changing map, i.e. to the highest possible gear-changing points, if the accelerator pedal is pressed quickly. The transmission accordingly shifts down immediately by one or two gears (temporary downshift).
"Sport" mode activated:
The PDK transmission switches to a sporty gearchanging map and shortens the shifting times.
A sporty driving style is recognised more quickly and the gear-changing speeds are adapted to driving performance.
Braking downshifts are initiated earlier. Downshifts occur for small decelerations, even at higher revs.
"Sport Plus" mode activated:
In "Sport Plus" mode, the PDK transmission changes to a shift programme designed for driving on race circuits. 7th gear is not selected.
The gear-changing performance is enhanced significantly again compared with "Sport" mode.
Please see the chapter ""SPORT" AND "SPORT PLUS" MODE" on page 167.
1. Have you got the sport button pressed?
2. Have you been driving the car more enthusiastically?
IIRC the PDK transmission has several shift maps and it will switch between them either if it is told to or if it "learns" how the driver is driving. I think the transmission has more "maps" than there are switch positions. The maps control both when the transmission shifts and how firmly it shifts.
I have heard of cases where people take modern auto cars back to the dealer complaining that it's changing gear incorrectly. Dealer simply asks, "Has someone else been driving the car?". If the answer is "yes" then that's often the explanation; the car has simply learnt someone else's driving style. Eventually it will either default back to its normal mode or learn the style of the next driver.
Some extracts from a PDK driver's manual,
Select position D for "normal" driving.
The gears are shifted automatically according to the accelerator position and speed. Depending on the way the vehicle is driven (economical, comfortable or sporty driving style) and on the resistance (e.g. uphill), the gearchanging points are shifted towards higher or lower engine-speed ranges.
The accelerator position, driving speed, engine speed, longitudinal and lateral acceleration and the road profile all have an influence on the gearchanging characteristic.
When you brake, and depending on the amount of deceleration, the PDK transmission changes down earlier.
With a sporty driving style, downshifts are already initiated when the brake pedal is touched lightly. This further enhances a dynamic driving style.
The PDK transmission temporarily changes to the sportiest gear-changing map, i.e. to the highest possible gear-changing points, if the accelerator pedal is pressed quickly. The transmission accordingly shifts down immediately by one or two gears (temporary downshift).
"Sport" mode activated:
The PDK transmission switches to a sporty gearchanging map and shortens the shifting times.
A sporty driving style is recognised more quickly and the gear-changing speeds are adapted to driving performance.
Braking downshifts are initiated earlier. Downshifts occur for small decelerations, even at higher revs.
"Sport Plus" mode activated:
In "Sport Plus" mode, the PDK transmission changes to a shift programme designed for driving on race circuits. 7th gear is not selected.
The gear-changing performance is enhanced significantly again compared with "Sport" mode.
Please see the chapter ""SPORT" AND "SPORT PLUS" MODE" on page 167.
Thanks for the explanation Rockin, but the hesitation happens in normal, sport, sport plus, manual mode or auto. Wouldn't say it's the PDK as the engine is also pinking slightly under a light throttle as the hesitation happens.
I'd say fuelling or ignition related or maybe the emissions system having a fit.
Whatever it is I can see a battle coming on as the dealer says they can't fix the issue as there are no fault codes, even though they have driven it and acknowledge there is an issue.
I'd say fuelling or ignition related or maybe the emissions system having a fit.
Whatever it is I can see a battle coming on as the dealer says they can't fix the issue as there are no fault codes, even though they have driven it and acknowledge there is an issue.
Edited by ellesmereFNC on Friday 17th March 04:52
ellesmereFNC said:
Thanks for the explanation Rockin, but the hesitation happens in normal, sport, sport plus, manual mode or auto.
....the engine is also pinking slightly under a light throttle as the hesitation happens.
Hmmm. On my manual car if I'm going slightly up-hill at 40-45 mph in 6th gear I sometimes think I can hear it pinking slightly. I've talked to the OPC about this and they say, "no, a modern car won't suffer from pinking because the knock sensors will automatically correct the ignition timing if it's detected. And there are no codes." Anyway, I simply change down a gear on the odd occasions that it happens which obviously makes it go away. Just to clarify, this isn't driving in too high a gear and the gear indicator light certainly doesn't ask for a gear change anywhere near that speed. These cars will easily pull from 30 mph in 6th.....the engine is also pinking slightly under a light throttle as the hesitation happens.
The only other thing I would add is that in gentle driving you can occasionally feel when the fuel supply is cut in or out by the injection system. IIRC these engines do not receive fuel all the time, only when needed.
As regards PDK transmission this is interesting from, http://autoweek.com/article/car-reviews/porsches-b...
"PDK adds a trick coasting feature that automatically drops engine revs to idle levels when you ease completely off the throttle. On long downhill grades, for example, the engine will stay in coasting mode until you step back on the gas or shift. Porsche says this feature, combined with stop/start, helps the Boxster lineup see a roughly 15 percent improvement in fuel economy."
rockin said:
Hmmm. On my manual car if I'm going slightly up-hill at 40-45 mph in 6th gear I sometimes think I can hear it pinking slightly. I've talked to the OPC about this and they say, "no, a modern car won't suffer from pinking because the knock sensors will automatically correct the ignition timing if it's detected. And there are no codes."
The tech at my OPC said the same thing, but it still does it! I turn off the coasting function most of the time, I prefer engine braking when going downhill and into corners...saves the brake too!
Sometimes cars can try to be too clever...and trip themselves up...which is what i think is happening here, one sensor is reacting to a minor fault off another and trying to cancel it out. So knock sensor is altering the timing due to the pinking, which alters the fuelling, which the drops power, which could confuse the PDK software, which etc...Did I say I once knew an old woman who swallowed a fly!!!
Might sound like a daft one, but where are you buying fuel? There can be some pretty substantial differences between the way engines behave, and although they are often set up to run safely on regular unleaded, Super often helps, especially when there is a bit of transient pinking.
Haven't tried supermarket fuel in a long while, but last time I did a back-to-back of Morrison's vs. Esso on an engine dyno, I was stunned at just how much performance difference there was. Have avoided it even for road cars ever since.
Liam
Haven't tried supermarket fuel in a long while, but last time I did a back-to-back of Morrison's vs. Esso on an engine dyno, I was stunned at just how much performance difference there was. Have avoided it even for road cars ever since.
Liam
LiamH66 said:
Might sound like a daft one, but where are you buying fuel? There can be some pretty substantial differences between the way engines behave, and although they are often set up to run safely on regular unleaded, Super often helps, especially when there is a bit of transient pinking.
Haven't tried supermarket fuel in a long while, but last time I did a back-to-back of Morrison's vs. Esso on an engine dyno, I was stunned at just how much performance difference there was. Have avoided it even for road cars ever since.
Liam
I Dont buy cheap fuel, use Shell V-power and BP Ultimate...only had the car 3 weeks so only filled it twice and its now been in dry dock for a week now.Haven't tried supermarket fuel in a long while, but last time I did a back-to-back of Morrison's vs. Esso on an engine dyno, I was stunned at just how much performance difference there was. Have avoided it even for road cars ever since.
Liam
At least its keeping the miles down...apparently the Techs are now asking Germany for advice as they can't solve why its doing what it does...wouldn't of bought it if we'd noticed the issue on test drive!
Okay, update on my car. It went into Porsche Guildford today and chatting to the service chap it seems it is a known "feature". According to him it's due to the cam variator switching the cam profile to a high power one as you get on the loud pedal. Apparently they had a Cayman in last year with the owner giving the exact same symptoms. They had it it for 2 weeks, changed ECU etc etc, couldn't find anything wrong and found that other cars they had did the same. Then Porsche in Germany confirmed it was expected behaviour.
They're going to plug it into diagnostics anyway to check, and I also mentioned the PDK not shifting quite as cleanly as I thought it used to, so they'll take a look at that as well.
Given that the hesitation is so minor the explanation makes sense to me, but we'll see if they come up with anything else.
They're going to plug it into diagnostics anyway to check, and I also mentioned the PDK not shifting quite as cleanly as I thought it used to, so they'll take a look at that as well.
Given that the hesitation is so minor the explanation makes sense to me, but we'll see if they come up with anything else.
ellesmereFNC said:
Well our GTS now been at the dealer for 2 weeks, Germany involved but not sure yet whet they think it is...maybe they'll just swap it for a GT3!
Update on mine: dealer checked it over, no faults anywhere. I've driven it quite a bit since and I can still feel it occasionally and it's very very mild. If your issue is genuinely more noticeable (you have to really be looking for it to feel it on mine) it sounds like either your issue is different or that maybe your cam variator isn't "variating" quite as swiftly as mine i.e. not "broken enough" to trigger an error somewhere. As I said before, Guildford told me they went right round the houses for a couple of week with this last year on a Cayman and in the end Germany said "that's expected".Well we're now into week 3 of not having the car...just had the below from the OPC, so at least there is a problem, it's not normal and they are trying to sort it.
have spoken to our senior technician again regarding the progress and he has advised the following.
In the beginning we confirmed the fault with hesitation under part throttle and it seemed to occur between 2000 & 3000 rpm but was worse in sport plus. The initial thought was fuel starvation as the vehicle judders until it exceeds 3000 rpm. No relevant faults were showing in the system tester and in actual values the mid-range fuel trim was high but not enough to flag a fault.
During another road test using data logger a noticeable dip in fuel pressure occurred at the same time as the fault. We checked the low pressure delivery rate which was 4400ml over 60 seconds, this was way over the 2.91 minimum, we have tried a fuel pump control unit which has had no effect on the fault, we have replaced the high pressure pump and carried out the relevant adaptions but the fault remains.
We noticed 2 misfire counts on the 1000rpm per misfire section on cylinder 2 and also a timing retardation on this cylinder but not on any of the other 5, we removed the ignition coils and plugs but no visual faults found so we have swopped coil 2 to cylinder 3 then carried out a second retardation data log and found cylinder 2 now not retarding at all. We have sent all the data logs and screen shots back to Germany on the PRMS ticket and are now waiting for a response from them.
So a number of issues seem to have raised there heads...jus hope iits not to long to wait...boiught the car 6 weeks ago and actually had it on the drive for 3 of them!
have spoken to our senior technician again regarding the progress and he has advised the following.
In the beginning we confirmed the fault with hesitation under part throttle and it seemed to occur between 2000 & 3000 rpm but was worse in sport plus. The initial thought was fuel starvation as the vehicle judders until it exceeds 3000 rpm. No relevant faults were showing in the system tester and in actual values the mid-range fuel trim was high but not enough to flag a fault.
During another road test using data logger a noticeable dip in fuel pressure occurred at the same time as the fault. We checked the low pressure delivery rate which was 4400ml over 60 seconds, this was way over the 2.91 minimum, we have tried a fuel pump control unit which has had no effect on the fault, we have replaced the high pressure pump and carried out the relevant adaptions but the fault remains.
We noticed 2 misfire counts on the 1000rpm per misfire section on cylinder 2 and also a timing retardation on this cylinder but not on any of the other 5, we removed the ignition coils and plugs but no visual faults found so we have swopped coil 2 to cylinder 3 then carried out a second retardation data log and found cylinder 2 now not retarding at all. We have sent all the data logs and screen shots back to Germany on the PRMS ticket and are now waiting for a response from them.
So a number of issues seem to have raised there heads...jus hope iits not to long to wait...boiught the car 6 weeks ago and actually had it on the drive for 3 of them!
Maxym said:
Sounds like they should take the car back and do you a nice little deal on something else. Getting a 981 in a spec you like could be a challenge but there could well be something within that dealer group...
We're beginning to think the same...money back or an attractive deal on something else...we went for the GTS as it was more special than an S, but right now we wouldn't care about not seeing it again. Dealer doing what they can but patience running out with what is obviously a faulty car.Edited by ellesmereFNC on Wednesday 29th March 12:22
I have a similar issue on mine, (manual, non S) more noticeable when you turn the PSE on. Accelerate up to 3k steadily, lift of and the accelerate steady again and you get what I've started calling a "Sneeze", sounds like a miss or brief stutter before carrying on as normal. Probably happens at different revs but much easier to spot at this range.
It's off into the OPC next week for them to have a look. Not sure where I stand with no warranty if they start claiming I need this and that changing but that doesn't cure the fault, do I still have to pay for those items even if it doesn't cure the fault, can I just request the refit the old part back?
It's off into the OPC next week for them to have a look. Not sure where I stand with no warranty if they start claiming I need this and that changing but that doesn't cure the fault, do I still have to pay for those items even if it doesn't cure the fault, can I just request the refit the old part back?
Guys, did anyone manage to solve this?
My 981 PDK is behaving exactly how other posters have described and to be honest it is spoiling the car for me, even though it is very subtle and not something a passenger would notice.
I'm not sure how to go about fixing it, personally it feels fuel or ignition related to me but I have no doubt that OPC will say "no fault codes, nothing wrong".
My 981 PDK is behaving exactly how other posters have described and to be honest it is spoiling the car for me, even though it is very subtle and not something a passenger would notice.
I'm not sure how to go about fixing it, personally it feels fuel or ignition related to me but I have no doubt that OPC will say "no fault codes, nothing wrong".
SkinnyPete said:
Guys, did anyone manage to solve this?
My 981 PDK is behaving exactly how other posters have described and to be honest it is spoiling the car for me, even though it is very subtle and not something a passenger would notice.
I'm not sure how to go about fixing it, personally it feels fuel or ignition related to me but I have no doubt that OPC will say "no fault codes, nothing wrong".
Hi My 981 PDK is behaving exactly how other posters have described and to be honest it is spoiling the car for me, even though it is very subtle and not something a passenger would notice.
I'm not sure how to go about fixing it, personally it feels fuel or ignition related to me but I have no doubt that OPC will say "no fault codes, nothing wrong".
Nope unfortunately we never got to the bottom of this issue, our dealer at the time based near Chester spent 4 months trying without and success to fix the problem that all their technicians agreed was present. Then one day they took in another GTS which did the same and their attitude changed.
Suddenly it was a characteristic of the car and they would do no more...so in total we were without our car for 16 week from purchasing it when we were handed the keys and told nothing more would be done...No Sorry for your trouble, here’s a toy car or umbrella as compensation, just a bugger of from the service manager...sales even had the cheek to email to tell us to forget the issue and enjoy the car. A car which we bought from then to take on a road trip down to Tuscany, but ended up going in our Audi A4.
So it still hesitates but maybe not as bad if I keep the oil level up, the engine can be heard to pink under load on 97 octane, with 95 if we hav to put it in it sounds like a tin can rattling.
The Porsche dealer near Chester have ruined our experience of the brand.
Hopefully the dealer near Wolverhampton will be better, as they seem to of been up to now...much better.
ellesmereFNC said:
Hi
Nope unfortunately we never got to the bottom of this issue, our dealer at the time based near Chester spent 4 months trying without and success to fix the problem that all their technicians agreed was present. Then one day they took in another GTS which did the same and their attitude changed.
Suddenly it was a characteristic of the car and they would do no more...so in total we were without our car for 16 week from purchasing it when we were handed the keys and told nothing more would be done...No Sorry for your trouble, here’s a toy car or umbrella as compensation, just a bugger of from the service manager...sales even had the cheek to email to tell us to forget the issue and enjoy the car. A car which we bought from then to take on a road trip down to Tuscany, but ended up going in our Audi A4.
So it still hesitates but maybe not as bad if I keep the oil level up, the engine can be heard to pink under load on 97 octane, with 95 if we hav to put it in it sounds like a tin can rattling.
The Porsche dealer near Chester have ruined our experience of the brand.
Hopefully the dealer near Wolverhampton will be better, as they seem to of been up to now...much better.
Thanks for replying, unfortunately your answer does not come as a surprise nor does the dealer - one who I refuse to give another penny to.Nope unfortunately we never got to the bottom of this issue, our dealer at the time based near Chester spent 4 months trying without and success to fix the problem that all their technicians agreed was present. Then one day they took in another GTS which did the same and their attitude changed.
Suddenly it was a characteristic of the car and they would do no more...so in total we were without our car for 16 week from purchasing it when we were handed the keys and told nothing more would be done...No Sorry for your trouble, here’s a toy car or umbrella as compensation, just a bugger of from the service manager...sales even had the cheek to email to tell us to forget the issue and enjoy the car. A car which we bought from then to take on a road trip down to Tuscany, but ended up going in our Audi A4.
So it still hesitates but maybe not as bad if I keep the oil level up, the engine can be heard to pink under load on 97 octane, with 95 if we hav to put it in it sounds like a tin can rattling.
The Porsche dealer near Chester have ruined our experience of the brand.
Hopefully the dealer near Wolverhampton will be better, as they seem to of been up to now...much better.
So what's next? Are you just going to live with the 'characteristic'?
I find mine is fine towards higher revs or when making good progress, it's the partial throttle in higher gears when negotiating traffic that its most noticeable. Considering a lot of my driving is motorway rush-hour it is evident the majority of the time.
Not mentioned yet on this thread, but could it be drive-by noise or emmissions regulations related? I.e a part of the engine map at certain rpm/road speed?
There was an absoutely huge thread on here a few years ago from a guy with a Cayman R, the engine misfired/hesitated continually at 3k rpm in a certain gear, and was finally confirmed by Porsche as expected due to emmissions and/or noise regulations.
There was an absoutely huge thread on here a few years ago from a guy with a Cayman R, the engine misfired/hesitated continually at 3k rpm in a certain gear, and was finally confirmed by Porsche as expected due to emmissions and/or noise regulations.
Olivera said:
Not mentioned yet on this thread, but could it be drive-by noise or emmissions regulations related? I.e a part of the engine map at certain rpm/road speed?
There was an absoutely huge thread on here a few years ago from a guy with a Cayman R, the engine misfired/hesitated continually at 3k rpm in a certain gear, and was finally confirmed by Porsche as expected due to emmissions and/or noise regulations.
Sounds plausible. Motorbikes (almost universally) suddenly got a flat spot at 5500 rpm when stiffer noise regulations were introduced (quite a long time ago now). There is a dip in the torque curve of all 981 engines at 3000rpm which may point to the same conclusion. That said this issue seems to be limited to GTSs. Anyone with an S or 2.7 have the issue?There was an absoutely huge thread on here a few years ago from a guy with a Cayman R, the engine misfired/hesitated continually at 3k rpm in a certain gear, and was finally confirmed by Porsche as expected due to emmissions and/or noise regulations.
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