I was reading the recent thread about engine sputter and it lead me to bring this one up which I am experiencing but do not know if it just my lack of familiarity with my new 996tt. Here's what happens: Sometimes at moderate speed- 3-4k rpms; 50-80 mph, when I back off the throttle or just in sort of a coast-mode, it feels like the engine is 'mis-firing'. However, it accelerates fine, idles smoothly and just passed CA smog with incredibly low emission numbers. It runs fine but has this zone where it feels sometimes like it is hestiating.
It almost feels like a vapor lock or I sometimes suspected at first that I was just feeling the differential slip/wheel shift, wastegate release or something. The PPI done 1500 miles ago show all is OK.
Any ideas?
David

 

sounds like the vario cam? do a search and see if that sounds like it.

- chuck

 

Thanks Chuck
I searched and saw a few mentions of the hesitation between 3-4k rpms related to the vario cam. That might be what i am feeling. It doesn't feel like a mis-fire in the classical sense- it does feel like something mechanical that is 'inbetween' things.
Someone else though said their vario-cam transistion sounded like a 'scratchy sound' mine's no sound at all- but a feeling like a slight thud or push/pull if that makes sense and why I thought it might be a vapor lock or the diff. It is right in that rpm zone though and I beleive I could make it repeat almost anytime. Push the throttle and it just blares into the horizon and it idles smoothly- quite unlike an ignition problem.
moe comments welcomed

 

I've experienced this also. It's not persistent so I never looked into it. It happens about once a month, may be less.

 

In notice the slight hesitation on the way up thru the rpm band, but never when coming back down....but I agree with the variocam suggestion.

 

what thread are you guys looking at for the vario cam problem?

 

I searched 'vario cam noise' and others in that ilk; but here's one
https://www.6speedonline.com/forums/...cam+transition

 

Yes- mine is on the way up, not down but more in 'that zone' if that is the best way to describe it. While i said I could get it to repeat, I may be wrong because it idd seem to disappear or happen randomly- even though I knew where it ocurred in the powerband. Need to observe more now that i have this input. thanks everyone for your input- more is always welcomed.

 

Lightstream: You're corrrect when you say you can't detect it all the time...and it occurs in that 3500-4000 rpm band. It seems that sometimes it's noticeable, but most of the time the transition is seamless...

 

Hi Chuck
yes, that's accurate now that i think about: randomly seems to happen in that band.

by the way- is everyone's short shifter 'notchy' - like you are clicking/plunking it into gear? very different than the regular shifter- feels like more like an unsynch'd shifter in a formula car on upshifts. As I said, i am getting the feel of the car right now and value all your input. getting the feel is certainly a pleasant experience but if I have a problem, I'd rather like to know.
David

 

Did you have the billet shift linkage installed? If not, it maybe the PLASTIC OEM linkage shredding into pieces ...

 

From the threads I looked up onthe subject youhave just bropught to my attention, it seems I might just need an adjustment. i kind of like the way it feels- like it is snapping into gear- but most people would call it notchy. If I am wearing down the linkage- better deal with it. I'm glad i asked- I have no idea what they are supposed to feel like.

 

sorry Ari- i didn't answer your question. this is a factory short shifter

 

I had the variocam problem. Was a broken bracket which kept the cam from changing and threw CEL lights. A slight jerk and then check engine light is what I remember. Easy fix.

g-luck,

David