RPM jump at 2.3K???
 

I have a 1998 boxster 986 that is completely stock, 55k mileage. I have a problem when the car is cold at constant acceleration I get a jump in rpms at around 2,300 rpms. It revs normally and then once it hits 2300 rpm it almost drops too 2200 rpms and continues to go up. I don't know if this is a transmission or clutch issue. It is a automatic tiptronic and has been garage kept for quiet some time. I also have been having trouble between gears but when car is warmed up. From fourth to fifth gear (car is automatic) the engine revs up in between shifting. Like the accelerator sticks when the clutch engages trying to problem shoot this, other than that the car runs like a champ. If anyone has a idea as to what this is I would greatly appreciate any pointers. I am in Denver at high altitude, don't know if that would affect it but car came from Tucson, AZ two years ago when I bought it.

I've experienced the same thing and I dug up the answer that I found previously.

http://986forum.com/forums/general-discussions/2485-tiptronic-tranny-hesitation.html

03box said "Hey guys I stopped by the dealer today and talked to the service director and he said that what I am feeling is the vario-cam. He said this issue comes up all the time. He said the reason I only feel the change in 2nd gear is because the torque load on the engine is totally different than 3rd,4th,etc. He also said that for some reason it is more noticeable in tips than in manuals. He said the cam is moving to a much higher lift to gain extra HP. I have had two dealers tell me the same thing."

Seems like a normal occurrence on these motors/transmissions so nothing to worry about. As far as the transmission slipping in between 4th and 5th I've had this happen to me a few times as well. The car tries to shift then the rpms rise while the car coasts then it finally makes the shift. It has only happened to me a few times in almost 2 years. This may be caused by low levels of transmission fluid so you may want to check that if it was never done before. My car has not done this for a very long time and I never touched the fluid level however. I have noticed if I try to accelerate the moment the car selects a higher gear it acts a little odd but that makes sense.

What you're describing is your Torque Converter performing as expected at that 2nd gear 2300 range. Watch this video;

Torque Converter Movie - YouTube

Issue between 4th and 5th? Sounds like its time to service the transmission.