If your idle seems to go up suddenly several 1000 rpms and then back down to normal after a few hours and there is no vaccum leak you should clean the contacts to the Throttle Position Sensor! Thats what caused my seemingly random problem.
Gotta love that! Steve, when can we see new paint?
Glad you fixed that nagging problem. I've had so many electrical gremlins with my Z at times it has driven me insane. When it's running, it runs great. But when something goes wrong . . .
I had one **** problem that I couldn't figure out. Took it to my mech. The @#$# had me spend about $850 on needless parts before I yanked the car from his garage. None of this in for a penny @#$#!!!!!
Took it to my current mech, who I use only when I'm completely stumped, and he fixed it for $40. Turned out, the kid who I bought the car off of incorrectly installed the MSD ignition and it eventually fried (only after I owned the car). All my mech did was take off the MSD box and rehookup the stock ignition system.
But, if there's a bright side, I ended the affair with brand new injectors, fuel pressure reg, throttle pos sensor, AFM and ECU. Expensive!!! But I'm good for another 20 years.