Sorry about posting my question twice in two different forums. I replaced the crank position sensor (CPS) over the weekend and now my 1990 Buick Regal Custom with its' 3.1 liter V6 runs continuously without shutting itself down after 5 minutes or so like it used to. Thanks for the help! That was very very frustrating. The sensor only cost me about $20 dollars, but it sure wasn't an easy thing to replace. Just so anyone else out there may have this same problem on there 3.1 liter, the CPS is located on the passenger side rear part of the motor, above the oil pan and near the crankshaft pully. You will have to raise the car up and crawl underneath to see it and get to it. You will also need small to medium sized hands to get it off. It is held in place by only one small 10mm bolt. Be careful prying it out, as the plastic housing will easily break apart. I had to use Vise Grips on mine along with a long thin prybar just to get it to come out, because it kept dissentigrating on me. But after I got it out and replaced it, the car has been running fine eversince. Doing this job myself was well worth the effort and savings versus paying some inflated auto mechanics' labor charges (robbery) these days! Good luck