04 hyundai elantra gt

Lauro: Many people with your car are reporting a bad fuel pump. Read this Hyundai forum and you will see: http://www.topix.com/forum/autos/hyundai/T9BD2R6MGSRTSUS7V

Check for engine codes related to Camshaft Position Sensor or Crankshaft Position sensor. Replace as necessary.

Sounds not good. Question how long was car driven before it overheated. Next thing check your oil if there is a white milky kind of sludge in oil then you may blowen a headgaskit if thats the case you may need a new engine.

No codes would point to fuel problem such as low pressure.
Was the car left overnight at the shop so it would be a cold start for the mechanic ?

I would check the transmission fluid. It may need changed and the filter changed. Perhaps you are not getting a good spark from your spark plugs or coils. Has it been awhile since you had a tune up?

Your transmission fluid is dangerously low (tranny is dry). The pops & jerks are the transmission
internal components trying not to seize onto each other due to lack of lubrication and/or overheating.
Low transmission fluid leads not only to loss of lubrication but lots of overheating (of the tranny).
The loss of Elantra performance (speed tops out at 55), is caused by power loss due to friction inside the transmission. All your power is lost overheating the transmission (toward destruction), instead of
being transmitted through the transmission to the wheels.

The 2004 Elantra takes Hyundai SP-III Automatic Transmission Fluid, with 8.4 quarts used in a
total refill - but just 5 quarts at a fluid change. For How-to transmission fluid change instructions:

http://en.allexperts.com/q/Hyundai-Repair-815/2004-Elantra-GT-transmission.htm

www.autozone.com claims that 2004 Hyundai Elantra can take these non-Hyundai ATF's:
Lucas Semi-Synthetic Multivehicle ATF
Pennzoil Muilt Vehicle ATF
Valvoline Maxlife Dex/Merc ATF
Castrol High Mileage ATF

Your transmission is slipping which can cause a huge amount of damage both to the car and your wallet. Take it in for service as soon as you can.

IT COULD BE A NUMBER OF THINGS

check air filter,fuel filter,spark plugs and wires,vacum hoses for damage.with no engine trouble codes,these are the usual suspects.hope it could help!

sounds like the transmission fluid level is incorrect. Follow the instructions in the owner's manual. You'll need a funnel, rags, and Hyundai transmission fluid ($15 a litre in Canada)