Vacume Leak - High Idle ???

Can anyone shed some light on how to track down a vacume leak in a 4.0?
For about a year now i have had no idle in the morning when engine is cold, but high idle 1500 t0 1800 when warm? Also when you turn on AC the idle does not increase at all. If i pull the hose off the side of the air filter box it does not effect the idle at all? What about the vacume accumulator under the battery, is this a source of vacume leaks? HOW DO YOU TRACE DOWN A LEAK???
Gas is expensive in Oregon and i do not like supporting our friends in the middle east:flame: !!! Thanks for

I know that some say to use starter fluid and spray the lines and listen for a change in idle but I've never been successful with that method. Could be b/c the 2 leaks I've had have been far enough away from the intake for the starter fluid to have an impact on the idle. I found both of mine by just visually inspecting the lines very closely. The last one was the main line coming off the vaccum canister located in the bumper. That line comes in under the battery and I've heard it is one of the most likely candidates for a leak. I know that doesn't tell you much so I apologize. Let this marinate a while and see if some of the more experienced people have something to say.

The biggest vacuum "leak" on your engine, other than the throttle body, is the AIC--Air Idle Control--stepper motor. If you remove the air intake tube from the top of the throttle body, you'll see a large hole, just to the front of the opening to the throat of the throttle body itself. That hole allows air to bypass the butterfly valve in the throttle body--the valve that is connected to the skinny pedal you push to go. So if the AIC is not operating properly, meaning it does not shut off that hole just described, you get high idle. To isolate the AIC circuit from all other sources for a leak, block that hole with a plate. Your idle should drop to minimum immediately--to arround 650 RPM. If that doesn't happen, pull all vacuum lines from the manifold, one at a time, and seal each manifold port, again looking to isolate a whole circuit. You can't pull the the line connecting the MAP sensor to the throttle body, or the engine will die, so check that one visually very carefully for tears and breaks; however, if the MAP line is cracked, the engine will run very rough, if at all. If you still haven't found the leak, it probably is either the throttle body gasket or an intake-to-head leak; if so, spraying starter fluid arround the base of the throttle body and the head/intake manifold joints should affect engine RPM.

Thanks for the information! I will try this weekend!

Here's a less messy way....use an unlit propane torch.Point it at all the vac lines and connections(Don't forget about the power brake booster hose) When the gas is inhaled through the vac leak it will affect idle letting you know where your leak is.