Windstar Surging...Help!

I own a 2001 Ford Windstar. About 3 months ago it began idling rough. I read the codes and it turned out to be a misfire. I replaced the plugs and plug wires, coil pack, and fuel filter and fixed the problem. Ended up being the coil pack. About a month after that, i noticed that while the van started warming up it would have problems idling until it warmed all the way up. No big deal right? Well 3 days ago, the van started idling really rough. Rough enough to shake the vehicle. It would idle like this while sitting still no matter if it was in park or drive. I read up on this issue here in the forum. Another user posted some great links to DIY valve cover replacement according to Ford's TSB. I completed the work per the TSB and replaced the isolator bolts, cleaned the EGR valves, replaced the gaskets,and valve cover. This didn't fix the problem, so I took it to a shop and had them read the live data. They came back with the codes and suggested i replace the TSP and the IAC Valve. No problem, did that. Also cleaned the MAF while i was at it. Problem fixed, but now the vehicle surges while in park or drive and sitting still. It will idle real low and real high, back and forth between the two. I have also noticed the engine getting hot, but i think that may be due to the constant shift in idling. Any help or suggestions you have would be greatly appreciated. Sorr for the long post, and thanks in advance for your help.

Hi and welcome to the forum!

I would look for any vacuum leaks first. Specially the lines at the back of the upper manifold. That would be the most probable cause since you already took care of most of the components that could cause such behavior.

Oscar.

Thanks for the suggestion Oscar. Took it to a local mechanic and had them do a live read on the codes. They couldn't pin point the problem. They did spray the around all the hoses and manifold with carb cleaner, but the engine didn't surge or blow anything back. I read somwhere else online, that pigtail for the TPS can go bad and cause all of the problems I have been having. Had to order the part online and just got it in this morning. Gonna replace it tomorrow and see how it goes. If that doesn't work, I'll try the O2 sensors and see what happens with those. I'll post the results once I get complete each repair.

If you don't have any codes indicating that the oxygen sensor are defective, they are most likely fine.
They are not a high failure item on the Windstar.

P0171 and P0174 codes are RARELY caused by the oxygen sensors on the Windstar.
The MOST common cause is a vaccum leak.
A vaccum leak being any air that enters the intake between the MAF and the intake valve.
The air pulled out through the PCV valve (front valve cover on 1999 and newer) is replaced by air that enters the rear valve cover (1999 and newer) through the "Breather" hose that connects to the big flex hose that goes from the MAF to the throttle body.
In short, the air that enters the crankcase through this hose is air that has passed through the MAF, and as such has been measured.
I would recommed that you check the PCV line and the "breather" line...making sure that they are not cracked, broken or disconnected.

Also check the IMRC links to make sure that the IMR shafts are both connected to the actuator.
On the 1999 and newer windstars, 1 electrical actuator drives both of the shafts.
It is common for the nylon clips that connect the shafts to the linkage to break, or otherwise fall off.
This leaves 1 or both of the IMR shafts to flap back and forth, causing the intake into 1 or both banks of cylinders to be incorrect.