I've had my manual-shift roadster for about a month now and every once in a while I'll back it into my driveway. It has a very slight downcline to the road. Today I backed it in, parked it, turned it off and left it in reverse without setting the parking brake. I was sitting in it getting my stuff together to get out when I felt the car start to roll forward slightly. It would start, stop, start, stop and then it started to roll and pick up speed. I stopped it and set the emergency break this time. I've parked it like that before but this is the first time this happened.

Is this a problem? I've been driving manual-shift cars for nearly 20 years and never seen this happen until now but all manufacturers are different. I wouldn't think a car should roll forward while in reverse without the clutch pushed in.

I called the dealer to see if I should be concerned but they refused to speculate until they saw it happen themselves. They said that they would have to compare it to another Z-car.

Has this happened to anyone else?

 

My driveway is sloped as well. I always park there to wash / detail the car (2004 6mt roadster)
I've only had mine a couple of months, but I have never had any motion like you describe...
It sounds like your engine is turning over (unlikely with the compresson, unless it's really steep) or the clutch is slipping... plus you had it in reverse!
I am mystified

 

The driveway isn't steep at all. I took it out again and got back a little bit ago. I parked it the same way again but the car didn't move this time. It has me worried a little bit. I'm going to have to keep an eye on it and remember to set the parking brake from now on. It won't do any good to take it to the dealer unless I know I can show it happening. there was no sound coming from the car the first time it happened. No grinding of gears or anything like that. It has less than 900 miles on it.

 

When the car is off it doesn't matter if it's in a forward gear or reverse. The transmission is hooked up to the engine and that is what keeps you from moving. I guess your engine turned over backwards! Definately strange. Sounds like a good one for the Car Talk guys. You should give them a call.
rich