for over the past year i have had a problem with my 95 lumina with the 3.1. my car will start up and run fine and you can go as far as you want, but when you shut it off and the the car sit for about 45 minutes to an hour the problems start, the car will hardly run and misfires and sometimes stalls, (im not talking a mild misfire either, the car fights to stay running.)if the car stalls sometimes it wont run again for about a half hour. after the car runs poorly the car straightens itself out and will run fine again and you can drive as far as you want again untill you turn it off again. the car never throws a code and ive been throwing parts at it and im getting frustrated.now here comes the list of parts i have replaced, ac plugs and wires, new fuel injectors thinking i had leaky injectors, a new fuel pressure regulator, new O2 sensor(the upsream because i only have one because it a 95 and its O.B.D1) new fuel filter, coil packs with a ignition control module, throttle position sensor, and thermostat. thats all i can think of at the moment. the car only has 46,000 miles on it. i replaced the lower intake gaskets at 39,000. the problem started at around 44,000. if i drive the car and turn it off and let it sit for a couple hours the car will start right back up, it seem to be within a period of time.ive discussed this on another forum and ive had no help. it sucks because i cant figure it out and im a mechanic myself. if any of you have any suggestions i am all ears. thank-you

Have you checked your lifters for proper opperation? You could have a bad lifter. I had this similar problem with another vehicle and have also diagnosed this with other vehicles as well. Has this already been looked at. Note: you probly know that lifters will prime when oil is supplied to them but in this case it sounds like the lifter is loosing its prime after it has sat for a little ie. when the eng cools the oil thickens a bit and this assists in re-priming the lifter or lifters. If there is a weak lifter this can be your problem. Not shure if this will help any but just a suggestion. Good luck.