I am having an issue with a 2003 Ford Windstar. Approx 218000 miles on it. Lately and very randomly when coming to a stop the vehicle will buck a couple times and stall. To me it feels like when you left of the clutch in a manual while stopped. It starts right back up and usually drives fine, but sometimes will almost stall or stall at the next light or stop sign.

The very first time it did this to me was pulling into a parking spot and it stalled, started right back up, but on the way home after it I got a check engine light with a code that mentioned IAC understeer (can't remember exact code) I first cleared codes, but it came back. I replaced the IAC with a new one and have not had that code come back.

Currently I have no codes when I read with a scan tool. Both stored and pending codes are no faults detected.

Car seems to idle fine and runs fine. I haven't done the calculations to be sure but may be getting lower MPG then in past.

I am leaning towards an issue with the TCC solenoid. I have checked the transmission fluid and it is still red and no burnt smell. I changed the filter and fluid at 196000 miles. Nothing odd in the pan. I have an Actron 9185 scan tool. I have also picked up a bluetooth obd2 adapter to use with my cell and the android app torque to try and log to see what is going on when it does happen. Of course it has yet to happen since I got it setup.

Any ideas?

 

Try the app "car gauge pro". It's $6, and is what I use at work, it gives an incredible amount of info with the Ford specific section.
From what you described, though, it does sound like a TCC lockup issue, which was a common issue. A TCC solenoid should fix it, it is on the valve body behind the side cover assuming you have an AXOD. I'm not sure it can be removed with the transmission in place, I haven't investigated that far.