cornic

Hello all. Really hoping I don't have a transmission issue here. Here's what I know so far let me know what other info I can provide.

2006 Turbo S

In any gear if I get much over about 50% throttle I start so notice a little bit of a vibration and skip sensation when driving. The Cayenne shifts perfectly fine and throttle response is good its just when I start to get on it this occurs. Do you all think it's a tranny slip or maybe the driveshaft is going bad? Any insight is appreciated. Also there is a slight burning smell outside of the car on occasion but its not too pronounced.

Thank you!

gbstu

I had something similar,under light load the engine was missing, turned out it was the coils. When were they changed last?

cornic

Not sure on last replacement, but now that you say it I did see the CEL pop a few times when i pounded it the other day and then it immediately went back off. Maybe it is the coils, I hadn't thought of that. Either way it's a cheap replacement I can easily do myself so I might start with plugs and coils and see if it helps as they probably need done anyways.

Thanks for the input!

cornic

I wanted to provide an update for others with this issue as well. The shop I took this thinks it is a knock sensor that is faulty or perhaps not plugged in all the way which is causing the computer to throttle back under acceleration or go into a sort of limp mode. This is based on codes the computer is showing. Going to get it serviced next week when they have time to work on it if this fixes I will provide an update. This requires taking the entire top of the engine off sadly and I think the previous mechanic didn't plug the sensor back in properly when doing work on the coolant lines. *sigh*

deilenberger

Actually it requires taking off the intake manifold. Someone good at doing it should be able to do it in about an hour.... sounds a bit like the shop is trying to prep you for a Porsche sized bill. If they did the prior work (replacing the coolant pipes) - they should be doing this gratis.

cornic

deilenberger thank you for the information. Previous work was done by a different shop before I purchased it. I do trust this shop so far they seem knowledgeable and fair but I will keep what you said in mind and bring it up before they begin work.

cornic

Welp back to square one I guess. The shop said the knock code didn't come back after being cleared and they didn't want to tear into all of it without being sure that was the issue. They couldn't replicate the problem. I certainly can. The car simply shakes under acceleration almost like it feels like tires slipping and regrabbing over and over, maybe that's all it is and I need to just forget about it! Not sure, it just doesn't seem right! Thinking of replacing coils and plugs anyways as it's relatively cheap to do.

jwicker

The driveshaft is easy to inspect. Get under the call, shake the driveshaft and see if it wiggles. You should be able to see the bearing support, so inspect it for cracks.

Turbodan

sounds to me like cardan shaft....common problem on these vehicles, as a result of another poor engineering design.

Shawn Stanford

This doesn't sound at all like transmission or driveshaft. It does sound like coils.

cornic

Appreciate everyone's insight so far.

So I got under it and couldn't really get the driveshaft to move at all, that being said I didn't have a lot of leverage as i didn't have it up on a lift or anything may put in on my ramps tomorrow.

Here is the best description I can give of the issue:

If I go say 75% throttle once it gets up to about 3k rpms it starts to almost feel like the engine or something in the front end shudders and power drops quite a bit, then it will _sort of_ recover. I can feel it in the steering wheel even. It doesn't happen all the time but about 90% of the time. Which is crazy to me that the shop couldn't replicate the issue. The behavior sort of varies depending on how quickly I get into the throttle. Sometimes when it happens the power just almost totally goes away until I get off the throttle and try to accelerate again and it seems to sort of bounce back a bit. It literally feels like a front wheel drive car spinning out and jumping around if that makes any sense.

If I go like 30$ throttle nothing abnormal happens at any rpm. It's only under semi heavy or heavy accceleration.

At this point I'm pretty confident it's not a tranny issue and something related to the engine, driveshaft or fuel/fuel flow/coils plugs. I guess it could still be the knock sensor based on other reports of what happens with that. I was only able to get the CEL to pop one time when I was really getting into it, it came on for about one second then went back off when I was accelerating heavily around 70-80mph.

19psi

Are you sure this isn't just the traction control kicking in?

cornic

I'm pretty sure it isn't and I had that thought as well but I suppose its possible this car is new to me. Is it disengaged with the PSM button? I suppose I can test with that.

Turbodan

does it rev normal when in neutral?
does it make a difference if the car is cold or warmed up ?

Turbodan

why don't you go out with the mechanic and show him what it is doing? maybe your are doing something wrong or he was scared to rev it?