Engine Performance problem
1997 Ford Aerostar 6 cyl Automatic 20600 miles
The engine runs great except when it idles. When it goes to a idle it seems a little fast but runs ok until it suddely slows down and runs very rough loping along hardly running and surging if in gear. The instant I touch to throttle it runs perfect. If I let it set and idle in neutral it will smooth out briefly and then back to very rough. I took it to Autozone to get error codes and they are: P1443, P0136, P0171, and P1131.I just bought the van at a auction and don't know the repair history. HELP!