phsingl

appreciate the detailed post - assuming mine's fixed today (its @ dealer now) then its thanks to this thread that I could pinpoint the issue and explain it properly to the dealership.
I feel your pain as its clear to me that Porsche (like most brands today) has decided that by doubting customers is a more profitable strategy in the first instance. Possibly the success of the marque in the Cayenne/Panamera/Macan era means they are getting more people showing up with warranty/CPO cars with non existing issues due to operator error as they are not enthusiasts in any shape (although I guess they've been selling automatic 911 cabs for some time which might fall into same category...)

the 958 is my 5th Porsche (3 911s and this is my 2nd Cayenne) probably going to pickup a mid 2000's Boxster for a weekend project car this summer because I still do like the brand on balance. I still have my 997 TT as well.

John Young

One thing I'm wondering about for the loss of power- we are all supposed to be on boost, but it loses boost under load(where the boost is supposed to be). Typically that is hapenning between shifts, or flooring it at higher speeds on hills should generate the boost since the car has significant load. We have all done the DME flash, TC changes, spark plugs etc. But I was thinking about this. For the CTT- and for a lot of german cars- the cheap diverter valves fail over time. Reading promo material from aftermarket manufacturers (a little biased to get you to change the diverter valves), maybe this is all just a boost leak in the diverter valve? Its a simple spring release and in a high temp plastic housing. Anyone switch to the agency power etc diverter valves on the S or GTS? It seems easy enough and is around $200 to $275. I hear the CTT or others say that it makes boost stay on more consistently- ie doesnt leak the boost away. Most people are changing this when they hear a whistling noise that indicates the spring or housing has gone bad (not a BOV sound), but I'm sure there must be a slight failure before that occurs that you cannot hear.

Any opinions on this? I may buy a set sometime. So far car is doing alright- I have a 15CS- but I do notice the boost drops quite a bit between heavy foot acceleration, and was wondering what could keep it dropping just slightly. I.e 4th at 8psi-11psi suddenly drops to 3psi in a 5th upshift (Normal mode selected). Not sure if thats due to the upshifts before being at higher rpm, or a leak. I have not leak tested the turbo system either- which seems like a PITA to get to compared to my old WRX, Eclipse turbo etc that I owned like 20years ago.

deilenberger

I think this is a generalization that hasn't been proven true. Many of us with CTT's are driving around perfectly happy with the plastic diverter valves. Just because something is milled from "billet aluminum" (a block of aluminum) doesn't make it better - but it probably makes it more expensive so it must be better right?

John Young

Thanks for that feedback that its typically not an issue on CTTs. Plastic is fine- my concern is more about the internal spring over time, and most BOV/ Diverters are about the response time of the spring, so you change out the springs with different spring constants to get faster closure between boost release levels. Exterior housing is honestly probably cheaper for a small company to machine- but making a real high tolerance plastic mold with associated tooling actually costs more. Some designs allow also for compression of the spring to change the rebound of the valve. Most of my cars have always replaced the base units with aftermarket, but those were usually higher boost levels than factory, and with race applications I wanted to ensure I did not damage the turbo when getting off the gas, but during shifts also had the fastest response that lost the least amount of boost.

CarGuyNVA

But.....isn't this loss of power problem with the 958.2 V6 twin-turbos something that's plagued even new vehicles?? Given that, I doubt this specific problem is related to bad diverter valves given the 'new-ness' of the vehicles? Besides, I thought the factory software release fixed this problem anyway...no??

Or are we talking about something else now...some other loss of power issue?

Mrg02D

Got this issue too! Just got a CPO 2015 Cayenne S with 44k miles.

Drove it 440 miles this weekend and had frequent loss of power on the interstate. I’d have to floor it down to the kick down switch to get it to boost and give me passing power. RPMs don’t increase with throttle. If I downshift, I’ll get a little boost but this quickly drops to zero again.

This has begun happening around town as well, though less obvious if I have sport mode on.

Im scared to pass now! Going up hills with cruise control sees a drop in speed, about 5-10%.

golftime

Definitely a classic symptom of the software update. Once it is done, it will feel like a different car.

rdboxster

Agree get the software patch installed. Really surprised the vehicle has been driven 44k miles without it.

Mrg02D

Yeah, I am too. I guess the original owner was a sloth and didn’t care. I’m no sloth, I have a Boxster also and lay on it pretty good :-)

Im also finding swirl marks and stuff that make it look like the old owner was more of a pendejo.

It was behaving yesterday. I am about to drive back today, so we’ll see. I’ve alerted my dealer and will see what they say. Definitely want the software fix. Anyone done the sports plus upgrade?

-Matt

rdboxster

The other item to check on is the transfer case. Long thread on it. Very common.

Mrg02D

Oh yea, I know about that one. It seems to be fine, no issues that I can detect.

edit: Dern, getting a bump when I start off from a stop! SOB! Dealer knows of the software fix, can’t see me for three weeks!

dbonds

I see your 44k miles without the patch and raise you another 13k miles. :-)

My "6 week old to me" 2016 Cayenne S (with ~57k miles on it) had exhibited a couple of what I felt were "low boost" instances in my short time with the car, but yesterday I managed to make a ~25 mile drive with literally zero boost available for the majority of the drive. Stopping and restarting the car brought it back to "normal", but I did capture several instances of no-boost via cellphone video - see attached video for one of the repro examples. Boost gauge is top right - you can see when it downshifts to 3 from 8 when "floored" at freeway speed...and the resulting zero boost situation (and painfully slow acceleration).

Was at the local Porsche dealer this morning and had the software update applied. Their Lead Service Tech knew of the problem the moment I described the issue (and thanks to this thread, I had the exact bulletin data available for him).

Only drove it home afterwards, but car seemed more responsive. Have a much longer drive tomorrow so should get a better feel after that.

Interesting part is I just finally was able to obtain historical service records for the vehicle before I got it, and original owner complained of "sluggishness" in Feb of 2017 with 22k miles on it...

dbonds

As an update - ~350 miles later I haven't seen any repro of the low boost situations. In fact, I did notice a spike to 17psi of boost in one hard acceleration (speeding up on a freeway entrance ramp, which ironically is the exact same situation my "zero boost" scenario above was first noticed). I think max I'd seen prior to the software update was somewhere in the 12-14psi range - certainly no more than 15. Seems to be more aggressive on spooling up the turbos post-update. No noticeable change in mileage according to trip computer.

BrendonSF

I had the DME update and it solved the problem with boost dropping off

drdantheman1

Sorry to resurrect an old thread but my attempts at completely solving this issue on my cayenne have failed so far. Have had this issue, although very intermittent, since I purchased my CS. Transfer case changed prior to my ownership and I’ve been doing 10k interval fluid flushes. Spark plugs changed at 35k (I know, a little late), and now brought to dealer for software update only to be told that the car has no faults, drives like the other CS they had on the lot, and already has the most recent DME software revision. Unlike what posters have said prior to the software update, I do have full boost when flooring the pedal down to pass from highway speed, but it’s at part throttle where the boost seems to drop.

Only thing I can think of is the tires are worn pretty low, but are evenly worn and correctly filled with air.

Has anyone else had similar mid throttle boost loss after the software update?