Engine Performance problem
2000 Saturn L200 6 cyl Front Wheel Drive Automatic 165000 miles
The car surges at any speed regardless of whether the cruise control is on or not, most noticeable at low speed but still happens at highway speed. Does not change the RPMs. I have had the spark plugs, fuel filter, alternator, and mass air flow sensor replaced in the last 2 weeks and the problem is still there. After $260 of repair (for the mass air flow sensor), the last mechanic told me it was a torque converter! The computer has not thrown a code and I am running out of $$ and patience. Help!
Check and test the following below: Oxygen Sensor
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)
Sometimes, what feels like a hesitation is actually ignition misfire rather than lean misfire. The causes of ignition misfire may include: Dirty or worn spark plugs
Bad plug wires
Weak ignition coil
Wet plug wires
Coil and Rotor