I have a VY seriesII V6 auto. while sitting on 100KPH it is doing about 1800 RPM and it will jump up to about 2200 RPM for a second and back down again.
It will do it with or without cruise control on and only when hot. If I lift off the throttle slightly the revs will go up before dropping which makes me think that the motor is missing. The problem seems to be worse on a particularly rough section of road (about 200 kms long) and possible when under more load (head wind or towing 6X4 trailer).
any ideas ?
Sounds like the same problem I had with a vs a few years ago. After checking the error codes I spent ages getting things done on it, new o2 sensors, throttle body sensor, cleaned injectors, etc. Finally the last bloke i took it to reckoned it must have been in the computer and was going to borrow one off the wreckers to see if that was the problem but wreckers had none so that meant 300 odd bucks for a new one that MAY NOT have been the problem. Ended up selling the vehicle for a good price (cheap) and getting a vy. Sorry I can't really help you mate but this is all I know.
I got the same problem with my VY Exec. Mech said that its is not showing any problems or throwing codes. Only problem is the transmission seal on its way out but fluid levels are fine. Having a chat with him again soon and see what happens. I'll let you know if we find something.