996 uneven throttle response - input?
 

I have a 2003 996 with 70k. In normal around town driving there is a distinct hitch in the light to steady acceleration. It almost feels like the AC compressor is turning on and off. I turned the system completely off and no difference.

In the old days (on other cars I have owned) when you let off of the throttle, there was an actuator that kept the throttle from snapping shut and creating a bucking effect. This actuator "caught" the throttle and eased it closed. Does the 996 have this?

I have tried:

TB cleaning
Motor mounts (which made the engine much smoother BTW)
New air cleaner

Thinking about new plugs. Maybe one is missing and causing the "compressor on" effect.

Other than that, runs great with lots of power.

I have read posts on engine surging but that is not really what is going on.

Dan
Kansas City
2003 996 70k

At what RPM does this happen, 32-33k? Does it cycle when holding steady throttle? Have you cleaned the MAF sensor? Is the intake stock? Do you have a CAI or K&N replacement filter?

I bet it is your variocam. if it is at 3200-3300 RPMs you can really feel and hear it under partial throttle. Search words like "surge". there are some threads on other forums around this. it is very noticeable in my car. Completely normal, yet can be annoying at times

I'll pay more attention and see if it happens at the same spot. Seems like it happens around the same spot depending on throttle position. If this is the variocam, it is pretty intrusive versus a normal car, but then this is no normal car. Getting that kind of power out of a package that size is bound to have a few compromises.

I realize my boxster is different but it doesn't have this at all. Will keep looking...

Dan

Dan,

I understand exactly what you are referring to (the experience itself.) I came from a bunch of cars that had a mechanical throttle, so going to the 996 with e-gas was a bit weird.

It took me a few weeks to really understand it because I had treated the throttle like a mechanical part. You kind of have to figure out the system, kind of like a black magic. I don't have the Variocam kicking in at the specified RPM range anymore so it does take some time getting used to.

Mike

One thing I always like to do is to check for vacuum leaks, which can cause annoying problems like these. I've got an article on using a smoke machine (very useful tool) here for the 996. That would at least rule the leaks out before you start replacing expensive parts:

Pelican Porsche Tech Article - Finding Vacuum Leaks on the Porsche 911 Carrera - Porsche 996 Carrera (1998-2005), Porsche 997 Carrera (2005-2008)

-Wayne