engine sputtered...stopped car then started again, the engine revved and accelerated..was able to get car to slow...drove about 200 yards process repeated...but did not accelerate. I was able to drive home. Mechanic says it has a PO300 code but the car is driving fine. I had driven the car up a steep grade to and from and errand. I had a similar incciden occure several years back when I parked the car on a sleep incline...it misfired but resolved. Any ideas.??