Toyota Repair: 2000 Camry V6 - Low Idle, camry v6, carbon buildup

Question
Hello,
Over the past month the engine idle speed has significantly decreased from about 1.25 rpms to .500 rpms. Sometimes I have to crank it 2 to 3 times before it finally turns over. I have kept it in pristine condition and have had dealership maintenance done at every interval.  It currently has 70,000 miles.

Before I spend $75 for a diagnostics from my local Toyota dealership I was wondering if you could give me a rundown on the possible culprits of such a problem.  I am a home DIY mechanic and would like to fix it myself if possible.

Answer
A common problem is the idle speed control valve, it's located below the throttle body which has to be removed to get it off, once it is off it can be cleaned with a throttle body spray cleaner,there is carbon buildup inside the valve which looks like a small revolving door, this controls the bypass air through the throttle body and controls the idle speed from an input signal from the computer, if the moveable door sticks it can cause idle problems.