This is no doubt from the cold.. and my Mazzy is shitbag asshole, if it were an animal it would be a cat.
Car: 2007 Mazda6S 6spd auto - 3.0MZI V6 (pretty much a Ford Duratec)
This is a problem on cold, COLD, starts. Ambient temp in the range of -18 to -24*C. On initial start RPM spikes to 5000-5500. I know cold, winter, starts will rev high, but this was almost flat out.
I let the car idle and warm, RPM gradually came down to ~1800 and coolant temp was at prime operating temp.
While driving I basically don't have to worry about using the throttle. It accelerates on it's own and maintains speed when going up hill. When I slow down and it puts itself in 2nd gear range, it jumps and lunges between 1st, 2nd, and 3rd and RPMs jump.
Because of it's 'self' acceleration (read: unintended accel.) I put it in neutral when wanting to slow and stop for traffic/red lights, when in neutral the RPMS are constantly jumping from 1400-1800 (will include video at end).
This happened twice today, once this morning when I went to get a coffee and then again on the way home. When I got back in my car and started up again after getting the coffee, everything was fine. Same with on the way home, I drove about 8km and really started to feel like I should pull over (especially when it was lunging between gears). Let sit turned off for a few minutes, started up and everything was right as rain and I drove home.
No CEL and no codes.
If the video links don't work let me know, tinypic.com distorted them all to hell because I shot them in portrait.
My own idiot thoughts are vacuum problem.