Engine Performance problem
2003 Subaru Legacy 4 cyl All Wheel Drive Automatic 130000 miles
My 2003 subaru legacy is hesitating a lot when I initially accelorate. It doesnt stop hesitating until I reach about 25mph. Sometimes it hesitates at higher speeds such as 50mph.
I changed the upstream o2 sensor after a mechanic told me that was the code it showed. Now it hesitates less frequently (maybe every 3 or 4 red lights), but still happens. Any thoughts on what it might be?
Dirty fuel injectors (cleaning the injectors often fixes this).
Bad MAP (manifold absolute pressure) sensor
Bad TPS (throttle position) sensor
Bad or dirty MAF (mass airflow) sensor
Low fuel pressure (leaky fuel pressure regulator or weak fuel pump)
Vacuum leaks (intake manifold, vacuum hoses, throttle body, EGR valve)
Bad gasoline (fuel contaminated with water or too much alcohol)
Could also be an ignition system problem such as: Dirty or worn spark plugs
Bad plug wires
Weak ignition coil
Wet plug wires