I've had this problem for a while now and I would like to have it fixed for summer. When my mustang is cold it does not like to idle, in fact I have to "keep it running" by revving it over and over for around 2-3 minutes before the stang will idle on its own. Once warm the stang runs great, never dies at idle or stop lights. I can shut it off let it sit for a while and start it right back up and she will idle. It's only a problem if the motor is cold. I have tried (and I might be doing it wrong) to check the TPS Voltage but got nothing.

Please help me out here.

The O2 sensors are "new" and they came with my x-pipe when I bought it. I would think they are good but I haven't (nor know how to) tested them.

I don't see the O2's causing a cold run problem, the system is running in closed loop during cold run. You could have an IACV that is failing, does the idle change appropriately when you fire up the AC when warm? I would be inclined to verify the temp sensor is also working properly.

I was trying to check the TPS voltage with a multi-meter by probing the wires, I never did get a reading off it and I'm really not sure I was doing this correctly.

The O2s came with the x-pipe and I believe the brand was doctor gas or something. I have checked the wiring and even followed it as far as I could see and the wiring looks great. Here is a link to my x-pipe, if you click on the image you can see the O2s.
http://www.badassmustangs.com/forums/garage.html;sa=view_modification;VID=1;MID=20

The timing is set at 14, if I remember correctly. I have tried to bump it down a little with no success so I put it back.

The only way I've been able to check the TPS voltage correctly was by cutting just the cover of the green wire (I think that was the right one) so I could touch the + probe to the wire and then touching the - probe to a ground.

Joe, I called my buddy and left him a message. He should call me back tonight or tomorrow.

As far as the Iacv, try pricing one at NAPA too, if you have one close. You may just find out it's cheaper there.

I tested the TPS (got a good reading this time) and it was at .95 volts so I set it to .99 volts. I took the mustang out for a spin and it seems to run great when warm, just like before. I'll start it up tomorrow and see how well it idles now.

As for the temp sensor, it was jumping around a lot and I don't know if I got a good reading off it. I ended up cleaning it plug and I may just replace it.

Any ways I'll test it again tomorrow and keep you guys updated.

TPS voltage really doesn't matter as the computer does it's baseline when it starts up. When I set mine I make sure it's below .96 and haven't messed with it in years. When it starts up it is in open loop for the first 90 seconds or so until the O2's and water get up to a certain temp and then it'll switch to closed loop. The O2's are being utilized the parameters for operation are a lot looser in open loop. Do you have longtubes or egual length shorty headers?? Do you still have the stock injectors or have you moved up to a larger size.
You're idle with the IAB disconnected should be about 150 RPM below what you're desired idle speed is. If you've got a cold air kit on the car those have been known to mess up the MAF reading at times as well.

I just had a crazy idea to look in you garage to see what you have.
I'll bet your idle is bumpy with that cam. Is that mass air meter calibrated for open element air filter??
I had similar problems when I first got my LX, it wasn't long before I got a Pro-M and no longer have those issues.

If it is a fox body it is not in the location on the pic, leastwise mine aren't. I think that pic is from a car as the upper intake manifold is backwards. Foxes have them on the tube that goes to the heater core.

I can get a pic tomorrow night.
Here's a wiring diagram that might be useful.
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Ok, I tested the temp sensor last night and found that it was giving very low readings according to this chart:
http://fordfuelinjection.com/?p=28

So I bought a new one and replaced the temp sensor.  I have yet to test the cold idle because the motor was already up to temp. I plan on doing more testing tonight.

Sorry, forgot about the pic tonight.
Are you saying you have a plug that is not connected to anything??

Yes, I haven't found where that damn thing plugs into yet.

Where does this plug, plug into:

Ahhhh, I removed my A/C. I don't think I need it...

I picked up a big side job this weekend and didn't have time to test the new temp sensor, I hope I have time tomorrow to test it.