I new here and I've got a problem with my son's 97 Thunderbird 4.6L Automatic w/OD. My son got the car real cheap for having a new engine and trans, knowing that it had a drivability problem. My son got it knowing that it stumbled and died at idle after it warmed up. Now my son lake in the brain dept. for when he told me about it he didn't tell the whole story, but he told me about the stumble. The first thing I thought off the top of my head was the IAC and sure enough after checking the codes I got a P1504 - IAC fault. After starting a pin point test I found that the IAC tested good, but it was froze open, so I changed the IAC. Well, my son help me, and when my back was turned he put it on and plugged it in. We took it for a drive and it ran like crap. So I started checking it the next day, and I found that the plug wasn't seated, so sure it wasn't working. After fixing that problem, boy it sure was hard, I started it and it ran pretty good, checked for codes and had none. I then took it for a drive and when it finally got to operating temp it started running like crap again, stumbling, missing and dying at idle. I got it home, cleared the codes, ran the KOEO test and the only code was P1000. I ran the KOER test and it threw P0505. I tested every ting in the pin point test and everything checked fine. I did notice that taking of the PCV hose at the TB, it picked up the idle and smoothed out quit considerably. I thought, that maybe the EGR was stuck open, but it checked OK. Really started thinking about the timing chain jumping a tooth, or the trans operation causing the problem. Well today, I fine out the original owner had this same problem and bought a new engine and transmission from Ford, figuring it would fix the problem, but it didn't so he got pissed and sold the car to my son. Well that shot down the ideas I had, real quick, so now I'm back to square one. Now, I have a question, and it may sound strange but I'm not that much of a FoMoCo mechanic, I'm a GM mechanic, so no wise cracks, please? My question, out side of what might I be missing, is this. I heard that I have to drive the car, or something like that, to make the computer relearn that it has a new IAC??? Is this correct, how long do I drive it, or is there another way that I'm supposed to reset the computer, or is this a bunch of bull?