I have a 2000 Ford Windstar that has the infamous 171/174 fault codes. We have changed out the isolator bolts & port seals as stated in the TSB for these codes. I have heard of other vans that have this problem and still run fine. My van does not run fine at idle. After sitting in gear for few minutes, it lopes and then stalls. In addition to the work described above, the MAF sensor and the bottom intake manifold gasket have also been replaced. There is an acutator on the front of the throttle body (idle speed control acutator we think?) that if removed, then the van runs fine at idle.

Can anyone offer some advice on what could be wrong?

Thanks.

Is it on the top of Throttle body?...then it's ISC Idle Speed Control
If it's on the front then it's a a TPS Throttle Position Sensor. Both are mechanical devices
and have to be replaced after some time. They both are well known to go bad on 2000.
I replaced my TSP and cleaned ISC.

Rob, if these are not MAF sensor induced lean codes, you may have vacuum leaks around the IMRC throttle shafts. That's a bad thing since replacing the whole lower (aluminum) intake manifold is the only fix that I am aware. Have you removed and spray cleaned the MAF sensor with a good electronics spray cleaner?

Joel