Sputter, losing power, dead accelerator, barely will go up hill

My daughter just started having a problem with her 2000 hyundia elantra last night. She said it kind of jerked, then would barely go, like it was going to die out, and the accelerator didn’t work, and then it would come back and she was only driving between 30-40. Today she says it’s still doing it, on and off, and barely makes it up hills. What do you think it is?

Just about anything is suspect. How old are the spark plugs & wires? Fuel filter? Air filter? Someone need to check the fuel pressure, and check for exhaust blockage.

Is there a check engine light on?

I just noticed that i had put the wrong year, it is a 2004 elantra (we bought used in 2006 with 24k) She is in college, 80 miles away, and travels back and forth a lot, I have no idea if or when the spark plugs/wire were changed, we have owned it for 4 yrs and doubt they have been changed (80k+ miles on it), also not sure when fuel or air filter were changed, she mostly just gets/needs regular oil changes, so if it doesn’t get done there, probably doesn’t get done. And her engine light comes on for spells for over a year now, but they have not found a reason when we have had it in garage (sometimes they say it’s the gas cap) but yes right now it’s on again…

She just called, and when she drove it home from work tonite it didn’t do it, but did do it last night for the first time, and on her way there this afternoon… so weird, but I worry that she will break down at night…

Something real quick to check is if the fuel pressure regulator is hooked up correctly (typicaly attached to fuel rail with one other hose connected to it) if you remove the one hose it will run/not run just like you described.