I currently have an Anderson PMS Series IV tuner, with a basic tune... I can't find anyone around here to tune it for me; the nearest person is four hours away in San Anotonio.

Tried opening up the throttle body butterfly a half turn or so on the curb idle screw?  I know "it says" you are not supposed to do that, but I have direct experience with two that benefitted from doing that.  I think the bigger cams require more air than the idle valve can deliver.

When I had a Ford B cam my car like to surge more than to my liking. After researching it a bit I added an IAC adjuster plate and it worked like a champ I've since changed the cam to something a bit better suited for my needs and it works even better. I think Ford also used these as part of a TSB for idle issues.

https://lmr.com/item/LRS-9939A/1986-93-Mustang-50L-58L-Idle-Air-Control-Iac-Adjuster

[Edit] like Steve mentions about the IAC valve limitations, this plate adjusts to allow more or less air into the intake at idle irrespective of the IAC.

Last edited by Jeff in GA (10/09/2015 9:07 PM)

I will try turning the throttle body butterfly a half turn today, then set the TPS voltage, also I never thought about the fan causing issues, don't recall the brand it was thinnest one I can find to be able to run the supercharger pulley. I will try unplugging the power to see if it still surges... thanks for all the comments.

I used to race Fox bodies and there are a lot of things you can disconnect to make sure you are not chasing a bunch of demons.
Optional items to get the car idling:
IAC
EGR
O2
MAF

Disconnect all of them and your car should still start and idle. It won't be happy, but it will still work. If it doesn't, you need to bump up the curb idle speed on the TB. Remove the IAC and make sure it is clean, but that it works. If the surging magicly went away while in limp mode (due to the disconnected sensors, I would start looking at them as your source).

In my experience it is usually caused by the TPS and the IAC fighting each other. I have had two TPS sensors that worked, but had a dirty signal. If you watched the voltage as you slowly opened the throtle, it would jump back and forth instead of a gradual increase. I have had several IACs stick open, or get clogged with crud from the valve cover.

Don't rely on the tuner to "fix" and peculiarities of the EEC-IV, only use it to adjust your fuel and timing curves. The other items are fairly well managed with the stock tables.
BobN