First eliminate the IAC Valve, after engine is warmed up let it idle and Unplugged the IAC Valve's connector, IAC Valve will close and idle should drop down to about 500rpms or engine may even stall, either is OK.
If idle stays high then it is a vacuum leak, and now is a good time to check for it.
Remove 1 vacuum hose at a time and put your finger over the intake port it came off of, if idle drops down to 500 then you found the leak, follow that hose.
Brake booster has a check valve, it is the part that the vacuum hose hooks up to on the booster, the "elbow".
Check valve allows the booster to hold vacuum pressure when engine is off or if engine should stall while driving, it usually allows 2 or 3 brake pedal pushes before vacuum is gone.
You can test that by starting engine then turning it off, test how many pedal pushes before it gets "hard" to push.
Also remember when you are parking on a hill many leave their foot on the brake pedal after shutting off the engine, so that counts as a pedal push and does drain the vacuum pressure.
So when you got back in to drive and pushed the pedal it may have already been drained, from parking.
Last edited by RonD; 04-19-2015 at 08:48 AM.