88 Caravan 3.0 stumbles 10 seconds after coasting or stopping!

I have a 1988 Caravan 3.0 that has developed a problem where after you stop for a 10 - 20 seconds at a light or if you coast, the engine looses all power and all but stops. The engine may be running at 200
rpm if that and sometimes stalls. If you floor the accelerator it will continue to stumble for 10-15 seconds then will snap your neck when it recovers. Will run all day @ a constant speed of greater than 20 MPH with good gas milage and acceleration. Just don't coast or idle the engine! I have noticed that the fuel pump seems to labor when the van acts up. The fuel pump and the filter have been replaced. I reset the computer and have driven the car over 200 miles and the problem persists. I received a code 12 and 15 from the computer. The van does not have cruse control and I have been told the 15 is related to a speed sensor that is for the cruse control. Any ideas?
Thank you, Randy
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Yes the speed sensor is for the cruise control but has other functions as well. One thing it is used for is Idle. The speed sensor tells the Computer that the car is coming to a slow stop and it will require the AIS Automatic Idle Speed Motor to hold the engine RPM to prevent stalling. Repair that problem and clean out the throttle body really good, then take it from there to see if there are other problems.
Glenn Beasley Chrysler Tech
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.