Surging idle when in neutral and park

Dirty air filter, dirty throttle body...try 2 bottles of gas line fuel injector cleaner...has your car been parked for awhile? Heet gas additive will work on any low gas tank sludge that you may have. Hope this helps.

Sometimes that's caused by a vacuum leak near the manifold area.

Sometimes air in the coolant will cause an idle problem. Air will keep the air temp sensor from sending proper info.
Hope this helps.

If it's surging, make sure your radiator is full. Do a tune up, plugs, wires, etc. Put some fuel injector cleaner in your fuel tank. On a cold start the vehicle compensates for being cold by adding fuel. Once it warms up the computer tells it to quit adding extra fuel. If it is a bad sensor of sorts, check engine light should come on.

Do you know what engine scan data is ? Disconnecting sensors is not the way to find a problem ! What is the computer seeing as data input signals . Is the vehicle in closed loop fuel control , is the EGR opening when it shouldn't be , Is the PCM controlling the idle air control valve or is the vehicle drive by wire (electronic throttle control ?
005 Idle Speed Problems Idle Air Control Test
007 Idle Speed Problems Scan Data for Idle

replace temp. sensor

You might want to check the engine for a vacume leak.Once the rpm's drop it may have a big enough vacume leak to not keep it running under a load.

change your some sensors that can probably cause your engine to run rough, ask you local oarts store for more info...

put a throttle position sensor on the throttle boby this should fix the problem!

there are 2 things that usually cause this, one is a dirty intake idle control valve and the other is hard engine mounts, I would say that both most likely apply to your car. try cleaning the intake with the following procedure from Ford.
Here is the most common cause of surges and stalls and low idle rough idle, it is the idle speed control air-bypass valve and throttle valve (IAC for short), they get full of gunk over the miles and cause idle issues (stalls, low idle) like yours, Get a can of intake cleaner from any local parts store, not carb spray, intake cleaner, it is made by a company called CRC, remove the air intake hose to the engine, hold the idle high so the engine won't stall, then spray the can of cleaner into the intake while keeping the engine running, use at least 1/2 the can, shut down the engine and disconnect the battery for 5 minutes, then restart and complete a number of mixed driving cycles, town, freeway, stop and go etc., after a few days the problem will go away as the system will relearn to the clean intake.

Sounds like a bad IAC (idle air control valve/sensor) that controls your idle when going from throttle to idle. If bad your idle will act crazy and can cause stalls easily. Pretty sure that's it.