i have a problem no one can figure out,have had 2 dealers,2 computers and 6 mechanics try and everyone is dumbfounded.97 grand prix 3.8 nsc will randomly sputter and stall driving,idling whenever when it gets warm,may run fine for a month or two then do it out of the blue for a day or two,runs fine once it cools down,never throws a code.yeah know what u are thinking so wait a minute.here it goes.new battery,alternator,cam position sensor,cps,map,maf,iac,pvc,iat sensor,purge control valve and canistor,fuel pump,filter,all relays in car,injectors check to specs,new plennum,intake,lifters,whole top end done,head gaskets,cat,exhaust and new computer,all coils,icm,plugs,wires,entire cooling and ac system new,hoses,went thru wiring harness,yes new o2 sensors,tps,egr no leaks anywhere,vacuum is on he money,when car sputters have had fuel pressure guage on and it is fine,new fuel pressure regulator,everything,everything,everything is new,good parts no codes ever show and no one has a clue.no reason for this to happen but once it cools off its fine maybe for awhile,maybe a month so hey all advice is appreciated and if u fix i will send voucher for steak dinner,movie,bar tab,almost forgot new ignition wiring harness,speed sensor,knock and temp control sensors...all and every sensor is new

air filter? any blockage in the intake tract? any blockage in the fuel tank? spark plugs? interesting that there's no codes being thrown, though. any fuel lines crimped or crushed? any sharp turns in the fuel lines? I'm not sure what else there could be. man, what a heck of a way to be introduced to the board! LOL, lesse if we can get this hammered out for ya. welcome to the site.

Sounds almost like it is vapor locking when it gets warm? Have you tried another gas cap? Maybe the cap you have is defective or the vent hose could be clogged or bent? I'm with Richard thinking it has to be fuel related but I really have no idea.

My moms old 300zx was doing the samething and I think her problem was though once it got warm, the fuel pump wasn't pumping right and the fuel was getting warm in the lines so she had to get a new fuel pump but you said you have replaced the pump.

My neighbor just recently had a Mercury Grand Marquis that was early 2000 model I believe and it started to shutdown on her when you would make a right turn and then later it started doing it making left turns. The dealer charged her to diagnose it and then couldn't figure out what the problem was that was making it do that. She ended up trading it in for an 08 model a couple weeks ago!

I hope you get it fixed though because it sounds like you have a lot of time and money invested in your ride. By the way though, welcome to the board!

got it,finally.i had cut hose going to air filter and computer box and installed cold air filter,but,it was catching hot air coming off the fans and since i disconnected hose box that holds the pcm was not getting air flow so it was heating the pcm up and causing the stall.have run it up to 220 many times to se if it stalls and it does not,and now i remember that whenever it did the pcm was really hot.had changed out the engine wiring harness the day before i discovered the real problem,not a fun job.but it is good to go and thats why it never threw a code.i do appreciate the input and pass this on if anyone else ever has this problem.will post pics as soon as i can figure out how to do it,not good with computers