loss of power

vehicle ran fine the day before .today the vehicle will not go over 40mph

Do you have a check engine light?

Could be a transmission problem or one of the following below:

Oxygen sensor.
Catalytic converter.
Fuel injectors dirty/sticking.
Mass airflow sensor/Airflow meter.
Throttle position sensor.
Crankshaft position sensor
Knock sensor
Manifold absolute pressure sensor.
EGR Valve
Fuel pressure regulator leaking or defective fuel pump.
False air leakage.
Fuel contamination.
Foul/defective spark plugs.
Open spark plug wires.
Ignition coil/Coil packs defective.
Incorrect ignition timing.
Cap and rotor.

Note:If it doesn't apply disregard it and keep testing.

Just finished installing a used engine (75k) in my 03 Santa fe with 177k. The vehicle was driving and running perfect til i stopped and tried to accelerate. The engine was bogging down and would only go 20mph. With then trans in N it does the same thing, boggs down. No codes. What should i look for. Thanks

Thanks for the info. Found the cat converter was plugged. Cut it out now there is plenty of power. Thanks again. Tim