I'm wondering if anyone else with a V12 car and the 8-speed ZF transmission experiences a hesitation when pulling out from a stop. Sometimes it doesn't happen at all, other times it's as long as 2 seconds and the car slams into gear.

I'm thinking it's one of two things: 1) the previous owner, who removed the secondary cats, didn't tune the engine to account for the loss of back pressure, or 2) the trans needs a new filter and fluid. I already have a filter and fluid ready to go, and I can always reinstall the cats that were removed.

Assuming it's not one of those, what else should I look at?

 

I've noticed it in my 2016 Vanquish, usually when jumping on it during a rolling stop like creeping through an intersection to make a left turn. Like you say, it's not every time, but often enough that I'm now extra cautious in those situations. I was used to a hair-trigger response in my 2006 DB9 and wish the Vanquish was more like that.

 

Quick question, have either had the ignition coils replaced? Later V12 Engine likes to not share misfire issues via codes or rough idle. When accelerating from a stop light hard, with no sign of traction control intervention and that white Prius gets the holeshot then I would suggest it may be time to replace those 10 year old coils and spark plugs, regardless of mileage. The engine needs to run properly before you can condemn the transmission 1st gear take off should not be hesitant.

 

Thought I would weigh in on this topic.

Every high performance car I've owned or worked on with electronic throttle (drive by wire), regardless of manufacture, has these "moments" of flat acceleration and it's inherent in the factory tunes. I've tuned for a dozen years and saw it there. I've also corrected some of it out in torque management within the tune, then there is an outside product solution, past the tune, that some believe in (but not so much me).

First the tune part:

With electronic throttles, there are actually 3 positions at any given time, only one of which is controlled by the driver. I won't get into the gory details, but the 3 positions are:
Commanded throttle
Relative throttle
Actual throttle
These 3 are almost never the same at some given moments of acceleration. Here is an example from an actual tune I did and subsequent datalog:




Ignore the red arrow (used in another thread on another forum). Notice, that even though, at this moment, I was commanding 100% throttle, actual throttle was only 84% and relative (what the engine sees) was 71%. These differences get more dramatic under different conditions and cause the flat spot feeling described here.

There are products out there that change these 3 positions outside the tune without actual tune intervention. They are quite popular in the Domestic US marketplace, but one would need to inquire if these companies have anything that would work on the AM platforms. One such company is Soler Performance, Inc. I'm not a fan and have never installed one, especially on a tune I've done BC it creates some ridiculous throttle situations. But the ones used on stock tunes, users brag about the differences.

I can't post a link to Soler, but it googles easily.

Hope this give some additional insight.

 

I wanted to offer a way to @Kalepsis to test the throttle hesitation I proposed above.

I know these events really happen in the blink of an eye. You mention up to 2 seconds hesitation before the trans hooks up. If you can create a safe test where you're not in traffic, try to recreate the situation and during the hesitation and after you command full throttle, look at the tach. Do you see any significant RPM? Usually you can hear the engine is revving, or not. If you do not hear or see any significant RPM on the tach during the hesitation, then, it is as I've described above.

On the other hand, if, during the hesitation, the engine is free revving and trans is lagging hooking up, then you might have another issue which could also be a TCM tune issue.

All the Best,

 

Thanks for the replies.

When it happens the revs don't increase right away with throttle input, as you described above. It lags the throttle quite a bit at low RPM. But that's not always the case, sometimes it goes right away. So I guess it could be an unreported misfire, but it acts more like a vacuum leak or failing throttle sensor.

I'm going to have to dig deeper. Unfortunately I don't have any way to connect to the car's computer and there aren't any shops within an hour's drive that have a dyno or the ability to tune a throttle map.

 

Just in case…my wife’s macan s does this…I find it super frustrating…the car learns driving styles..and responds accordingly….goes from 1 to 7 in quick order…super economical I am sure but very frustrating when pulling away..have to bury the throttle to get it to go..i take it out for a good quick drive in manual..keep the revs up..and it goes back to how it should be..im not saying that’s your issue…but maybe..

 

Not to pour snake oil on the fire, but I do have a device on my R8 that helps with the lazy drive by wire implications. It plugs in between the gas pedal module to allow more sensitivity through adjustments. Mine is basic with just a few settings but other brands have many more settings. Did not research what brands might cover the Vanquish of this era (if any) but if available, this could help dial out your issue.

 

My 8 speed Evoque used to do the same thing. If you didn’t come to a full stop, it wouldn’t change down into first gear and then when giving it gas it would barely get out of its own way, or jump down to first and jerkily move off. A case of bad programming IMO. My later model Velar was much better. It was all about rolling stops…

 

What happens when you use launch control? And if you are able to do it multiple times to see if something changes.