I have Nissan Maxima 1996, everything is good as far as I know until recently it started stopping shutting off on the road, sometimes when am going at high speed it gradually decreases speed and come to stop. Help
Your first step is to get the car scanned for any codes as this problem could be due to any one of dozens of things. AutoZone, Checkers, etc. will do this free, unless you live in California or Hawaii apparently.
If no codes are present it’s still a guessing game but a failing fuel pump is a possibiity.
These can be a hit and miss propostion.
Based on the title of your question I was going to say a vacuum leak or Idle Air Valve problem but the actual complaint refers to quitting at high speed also and this would pretty much rule out those 2 things.