wkearney99

Anyone had off-the-line starting lag, particularly when only recently started? As in, mash the pedal and there's only partial power being delivered. There's a about a second and a half delay before power comes up. This has made doing a merge/cross in busy traffic a bit unnerving.

This being a '17 GTS.

I have not had the vehicle defaulted to showing the info screen on the MFD, but will change it. I'll try and look for the boost PSI if/when this happens.

It's not repeatable. I thought it might have been due to a recent start from cold. I've had it happen after starting, driving less than a quarter mile, stopping twice and then needing to do a fast left (from stopped) to merge into cross traffic.

But then yesterday it did it while making a left (also from stopped) after I'd been driving about 10 minutes. I went to make a left through a break in traffic and about half-way there just wasn't the typical amount of power being delivered. Enough that I got rolling and making the turn but nowhere NEAR the expected amount. I cannot recall if this has happened during right turns, but I don't think so.

I don't know if it's related to this thread or not.

pastorom

Normally based on your description, i wouldn't think they were related, but then you mentioned that this only happens from a stop, and on left turns, so maybe check this out?

https://rennlist.com/forums/porsche-...-s-normal.html

A few of us hear crunching/grinding noises on left turns from stops, and you don't seem to mention that, but maybe it's the same underlying cause (transfer case), just manifesting differently?

wkearney99

I've had a number of 4WD and AWD vehicles over the years, so I'm pretty familiar with wheel hop and transfer case situations. I've not, as yet, encountered that with my '17 GTS. It currently manages to make tight turns in slow situations without any noises.

I've likewise dealt with overzealous traction control systems intervening during unexpectedly hard U-turn situations. Talk about unnerving, trying to swing a U-turn very quickly on a highway and having the engine cut power on you. Didn't make THAT mistake again in my Grand Cherokee. Now, I understand why it was doing that, I was taking a vehicle at speed, braking hard, swinging through a left U-turn and mashing the pedal. The move put a lot of outward swing to the body and traction control was kicking in to try and 'save me from myself'. But very nearly got me rear-ended by an on-coming vehicle. Lesson learned, "don't do that".

When I took a Turbo S out on the PECATL track I was specifically looking to see how the traction control reacted in that kind of situation. It didn't go all 'nanny mode' on me like the Jeep.

In this situation I'm making a 90 left turn from a stop. I've had the lag happen on both level ground and slightly uphill situations. But not repeatably. The traction intervention on the Jeep was absolutely repeatable. If it sensed too much yaw it would cut power. This does not seem to be the situation here, at least not in a repeatable kind of way.

I'd gladly welcome some insight on how to best test/explain what's happening. I'm certainly willing to believe traction control/engine management is intervening to counter my driving moves. But the observation that it doesn't do this all the time makes me start thinking there's something else affecting the situation, like something defectively programmed but only in a really narrow edge-case scenario. This is why the thread about cruise control and turbo boost caught my attention.

gnat

Since it's from a stop, it's not the start/stop function is it?

Try making sure to disable it after starting the car and see if that has an impact.

Also try with Sport mode enabled and see if that changes things (that should turn SS off too so try them separately for better information).

wkearney99

No, I always disable auto stop. But, yeah, that could potentially trip up a lot of folks not expecting it.

I have not tried it with sport mode, as the change to shifts and higher idle aren't typically desirable for typical urban driving conditions. I'll try it next time I'm out.

I started thinking it was just a situation involving being a cold start. As in, the engine hadn't 'warmed up' enough and something wasn't 'ready' for the performance demand. But at what point is the engine/vehicle going to be 'warmed up' enough to take that out of consideration? Ambient outdoor temps vary enough that I don't think that's a major factor. If I had to guess I'd say the ambient temp range where it's happened has been between 38F and 55F.

I don't think it's a traction control problem. I'm leaning toward it being a fuel/boost problem because I do recall one or two situations where straight-line acceleration "wasn't quite right". It wasn't as obvious there because power applied in a straight line wasn't as 'important' as during a turn/merge situation.

gnat

My thought was more of the SS not functioning quite as it should (e.g. not starting quick enough after releasing the brake) rather than you not expecting it, but if you are already turning it off then it doesn't matter either way

I'd be curious to see what your boost gauge says (why can't we have that on the diesel!) to see if this is related to that other thread or something different.

Does it sound like the motor is spinning as desired or is it just not getting power (e.g. is it the transmission that isn't letting the power through)?

Take a spin on 495 or 270 late at night when traffic is down and give it a few good WOTs to try to reset it's learning and see if that clears things up at all. My diesel will act like you describe from time to time, but it is always after my wife has been driving it for awhile and it adapts to her more sedate style. A few good WOTs and some horse play brings it back in line though.

wkearney99

I'm the only driver. The pedal has two positions, when I'm out of the vehicle, and WOT. Well, maybe not always WOT but it certainly sees more than it's fair share of 'spirited' driving.

I hear you vis the start/stop. I don't know how it's supposed to be functioning, but the way it functions in mine is entirely unappealing. There's just no rhyme/reason to it. Oh, I get why, as there's all kinds of other potential demands on the engine (AC, alternator, vacuum, etc). For being stopped at a light I'd be OK with that. It spins the engine right back up when letting off the brake. But when stopping for a quick turn through busy traffic it's downright dangerous. (Which is not the situation I'm having for this thread, however, as S/S is always disabled when I drive it). Granted, the vehicle doesn't know you're not stopped at a light. But what's REALLY annoying is it's tendency to just DIE during the slow creep toward a light. As in, the light up ahead has gone red, I back off the throttle and coast toward the light. Still about a car-length back, but still moving, S/S cuts the engine and the brakes I then want to use suddenly lose boost. WHAT THE HOLY FNCK DID IT JUST DO THAT FOR? I mean, really? That's just eff'ing stupid! So, yeah, S/S gets killed every time I get in it.

The trouble with debugging this is it doesn't happen often enough. But when it does I'm typically making a quick move through congested traffic. Not exactly a time when I want to be gawking at gauges. Or worrying the vehicle will suddenly not provide the expected power.

I do have a Bluetooth OBD2 dongle. I may have to look into configuring the Torque app to do some data logging. I'll have to see if it can extract and log the boost and other throttle/fuel values...

gnat

Agree about paying attention to gauges during such times and that applies to trying to video too.

Maybe pick up a cheap small dash cam that you can mount on your steering column to do the watching for you? Then you can just review the footage after an incident.

wkearney99

I did some checking and Torque Pro has a 'real time chart' plug-in that can record data points.

https://play.google.com/store/apps/d...ltimecharts_v1

I don't know enough about what values the OBD connector can 'see' but throttle position (pedal and manifold), fuel rates and a turbo value appear to be present. I'll have to experiment a bit more.

Some short trips, however, did not lead to being able to repeat the problem. This both from a cold start (overnight) and then 10 minutes parked (after a 20 minute drive). So, yeah, repeatability is not guarateed for this, unfortunately.

But if I understand it correctly, I think I can configure Torque and the plug-in to default to collecting the data. I'll have to try it some more.

wkearney99

After watching the live charts in Torque I don't think it'd be worth bothering with a dash cam for this. The Boost bar gauge on the MFD is nowhere near 'real time'. It lags at least a full second behind and often misses boost intervals entirely. As in, gun the throttle, make the turn and settle into traffic shows, literally, no change on the MFD's boost line. None at all. Torque, however, shows the changes.

J'sWorld

deleted

CarGuyNVA

This was my thought as I read this, the previous threads about 958.2 GTS and S model power issues, apparently related to boost issues (or lack thereof). Unfortunately I don't recall any of those threads offering a resolution yet from the dealers, still investigating the issue(s). In fact one owner got so fed up he traded the vehicle.

I hope for your sake this isn't the same issue, but again this is what came to mind as I read through this.

wkearney99

I think the first step is determining if boost is or isn't actually happening. I'd like to find an app or PC program that can extract that info from the ODBII connector. The ones I've tried thus far appear to only be extracting vacuum pressure and I'm not certain that's the correct value to be tracking for this particular line of troubleshooting.

I'm sure there's more data being sent via OBD than the apps understand how to interpret. Has anyone come across a listing of what PID hex values Porsche sends on the OBD connector? If I could find the PIDs it might be possible to plug them into the apps and start logging the data.

STFW came across this link, which makes it look promising:
https://www.telematica-us.com/articl...le=obd_porsche

Most notably the entries for Wastegate position, Boost Pressure sensors and various ones for Turbochargers. The page mentions some parameters may not be supported on all vehicles, which is understandable. The question is which ones are supported on the 958's OBD2 connector?

Anyone have any experience extracting/logging this kind of info from the OBD2 connector?

CarGuyNVA

Here's the thing though, I'd take a step back and be looking at this from the perspective of this is a brand new 2017 vehicle with the full blown warranty....I shouldn't have to be going through all this nonsense with my brand new GTS!

Porsche should make it right, and doing all the investigation/diagnosis/etc. After all this isn't an '08 GTS with 100k miles on it where you're on your own. That would be my position anyway if it were my vehicle.

Of course if you just want to find out more about what's going on yourself out of pure interest as an enthusiast, I can understand that too. My 'tinkering days' are pretty much over for the most part though, I think I'd be headed to the dealer.

nodoors

If the dealer can not replicate, they are not going to do anything about it. Do you want a mechanic driving your car around for several days being told to rip every left turn they can?