2003 malibu automatic jerks to change gears but loses power going up hill

Check the vacuum modulator on the transmission for a cracked leaky vacuum hose.

toyota avanza
if the engine light is on there are fault codes to be read
these need specific diagnostic readers

when was it last serviced
going up a hill
would suspect fuel delivery issue then spark problem

Could be fuel filter. When you need more gas for power going up hill your engine can't get enough.

have you changed your tran fluid
if not check and see if it is burned or has a burned smell to it
have the pan dropped and change fluid first

it sounds like a wire is bad/ shorting out. Put it in a dark garage open the hood have someone start it while you look under the hood if they give it a little fuel you will see an arc from the bad wire.

i have an 86 dodge ram 50 that sputters when i step on gas going up hill after it warms up ive changed the gasket twice with no luck solving problem it runs fine in neutral but in gear under a load it sputters

good day, you may try to change the transmission fluid it maybe fried and needs to be changed. a good run will be noticeable, hope this helps, have a nice day

fuel pump is bad. they are under extented warranty from ford. take to dealer and "insist" they change it. there is service bulletin on this, but dealers often play "dumb".

Is the transmission fluid at the correct level?

Is it a standard or automatic transmission? If standard, your clutch may be slipping. While driving down a straight road, push the brake while still in gear and push the gas pedal as well. If the engine slows with the vehicle, the clutch isn't slipping. If the engine speeds up while the vehicle is slowing down, the clutch is slipping.
If it is an automatic, check the transmission fluid. You may be low and the transmission is slipping while under load, or the torque converter is slipping for the same reason. You may have a bad torque converter clutch switch, but the computer should have picked that up and made your "Check Engine" light come on.
These are the main reasons you would be losing power going up hills unless your engine isn't powerful enough to handle the larger tires on extreme hills. (It takes more power to turn a larger wheel going up hill since the vehile has to travel further for each revolution of a larger tire. Incidentally, have your speedometer checked. You will be going faster than what the speedo says since you put larger tires on.) Good Luck.