Reduced Engine Power and Stalling Out

Hello. I have a 2004 GMC Envoy V6 4WD. Over the past several years my vehicle has been experiencing problems with reduced engine power, my guess. My first problem was when i pulled up to a stop sign and stopped my car just shut off. i started the car back with no problems and went on my way. Several weeks later i had the same problem and the check engine light then came on. i then took it to the GM dealer and they replaced a sensor, not sure which one, and they said that should have took care of the problem. Well, as luck has it, my car shut down on me again about 2 weeks later. Took it back to the garage with the check engine light on and they cant find anything wrong with it. Had a 2nd opinion and they also couldnt find anything wrong even with the check engine light on. OK, about 1 year later im sitting in my driveway fixing to leave the house. i put the car in drive and hit the gas and the car would not move whatsoever. i then threw it back in park and then back in drive. i pushed the gas and the car would barely move. i then put it to the floor and the car wouldnt go over 25mph. after about 2 minutes of driving with it to the floor at 25mph it began to work fine as usual. My most recent occurance, i was driving down the highway and i could feel the engine begin to sputter as if it was losing power and the engine began to chimmy. after several seconds of this it stopped and drove fine. Since the dealership and other garages cant seem to find anything wrong with it, does anyone have any ideas for me? Thanks

has the vehicle been driven with a scan tool plugged in to it this way you could monitor live data and veiw freeze frame info a competent tech should be able to locate the source of your problem also i would take a close look at the crank sensor jethro

Im not sure if that was done or not. When i took my vehicle to the dealershiop they charged me around $80.00 just to hook it up to some machine to check the computer, or whatever they check. Does that device you are talking about need put in the car while it’s being driven? and is that something i need to request and will it cost money to have it done. i appreciate the suggestion, just dont want to keep sinking money into getting my car checked out when they cant find anything wrong with it everytime i take it in. And where would the Crank Sensor be located and what do i need to look for once i find it? Thanks.