Engine Performance problem
2001 Chevy Impala 6 cyl Two Wheel Drive Automatic 128000 miles
My Impala has 128,000 miles, but it has always been a very reliable car and we have been meticulous with the maintenance on it. Recently, there are small surges of power in the engine when you are slightly accelerating on any type of grade. Our mechanic, checked and there are no fault codes. He also did some research and thought that it might be some knob that controls the engine that has been known to get flat spots over time. He replaced that knob, but the engine surge is still there. At 100,000, we did a full tune-up on it with new spark plugs, fuel injector cleaning, etc. Any ideas?
Have him check the fuel pressure to rule out the fuel pump/regulator and also the items below
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)