Larry Cable

At least its not the Sun! otherwise the driver would be from Essex with perky **** and bum!

Dewinator

I had a stumble that got worse and worse until the engine started going into safe mode, took it to the dealership and it had a bad intake valve. They had her all opened up and showed it to me with the engine running, you could see it flutter instead of sitting at the position commanded by the throttle.

duxsi

Was your stumble at the same point in the rpm band?

oalvarez

The stumble sounds very much like the same type found on all the new 2015 Ducati Multistrada motorcycles (guess who owns Ducati?). At 2,500 rpm and in second gear, if one jumped on the throttle the motor would hesitate to respond for a few seconds, then it would quickly accelerate. The problem was indeed attributed to the fuel mapping in the bike's ECU which Ducati eventually corrected via a flash/up-map. The difference here is that all bikes of the model year were effected, not just some.

one-rennlist

It is interesting that Ducati chose to correct the behavior in question since these bikes now most certainly fail the noise emissions test. For those wondering how the Ducati Panigale S performs a Swiss consumer report replicated the noise emission test and found an astonishing difference in noise levels when performed at slightly higher speeds: 78,0 dB at 50kmph vs. 91,5 dB at 53-56kmph for the full acceleration drive-by test. This is 3 times louder!

oalvarez

it's my thought that the original fueling/mapping would not allow the bikes to pass emissions, because there is no way (absolutely no way) that Ducati intended to release a bike whose motor didn't operate anywhere close to intentions. it didn't operate properly, plain and simple, and very much like what the stumble on the 2014 P-cars.

Dewinator

I'd say it was worst at around that same point, particularly at low throttle settings, but it wasn't completely normal at other places, for instance in cruise control on the highway it wouldn't be able to hold a speed perfectly, it would kind of surge and waffle. If I stomped on it, it would go though.

duxsi

That sounds eerily familiar.
But sadly the lack of error codes continues to be our undoing...

Dewinator

Hmm my thought is while errors with timing and the like could cause rough or less than optimal operation, a noticeable drop in power is most likely to either be a lack of air or fuel. My first thought was a bad HPFP was the culprit (which they've seen at my dealership too), but it will cause a fault if it's providing less pressure than spec. There's no fault for the throttle butterfly valve loose or in other than the commanded position though, until it gets really bad and the engine senses a lack of power.

squid42

Anybody else at 32c3?

Listening to all the talks about how firmware is software that is crappy, doesn't work right, testing is all blah, updates are random.

They cover not just cars. Trains, train track control systems, heart pacemakers etc etc etc. Everybody here looks at the 911 stumbles and thinks "just another bug... can we finally see the source code. K thnks by".

duxsi

As it stands we have 3 solutions / theories.
1. Faulty intake valve
2. Plenum
3. S/W mapping

The fact that the stumble appears after x,000 miles with no apparent S/W changes or modifications to the engine, would lead one to believe that some component ceased to function properly (such as an intake valve).
PCNA will not touch the car with a barge pole, so what is one to do?
I suppose head over to an Indy for a compression test?

jadoca

Try Norman Taylor and Associates (818) 244-3905 no cost to you. They took care of a bike for me once.

pfan

I think we should add a 4th possibility - the VarioCam Plus system, along with it's numerous solenoids, sensors, and actuators. In addition, the system relies on oil pressure to actuate a number of valves. Could a momentary decrease in pressure or a slight blockage in a guide possibly cause an abrupt cam changeover?

I bet Elon Musk could solve the problem in a couple of days.

Archimedes

IIRC, Ducati never truly fixed the low range stumble. Lots of modern high performance bikes have it due to emissions and noise issues. I had a 2011 Multi S that fueled very poorly down low. I had multiple 'updates' that did nothing.

My Aprilia TV4R and RSV4 fueled great. Interestingly though, neither of them seemed like they could be legal from a noise perspective.

GraphiteGrey

Two people in the 991 GT3 forum today reported that they've had this problem and have fixed it by resetting throttle parameters.

Here is the thread in the 991 GT3 forum; note in particular comment number 20, which reports the fix, and comments 23 and 24, which report that the fix was effective:

https://rennlist.com/forums/991-gt3-...st-gear-2.html

Here is the reported fix, which is specified in comment number 9 in this thread:

https://rennlist.com/forums/991/8904...ion-issue.html