Engine Performance problem
2003 Pontiac Grand Prix 6 cyl Front Wheel Drive Automatic 112000 miles
3100 3.1 V6 Grand Prix, great car, very reliable has regular maintenance done. Within the past 3 months I have noticed a loss of power when you go to accelerate. The RPMs go up and it takes awhile for it to shift into the next gear. This past month I have noticed that when it does shift it then almost seems to miss or sputter and has very little power until you really give it the gas and then it seems to come out of it. It starts great and idels well. I have had new spark plugs and wires put on and last week had the transmission flushed and the filter changed and nothing has changed. What should be the next step?
Lacking power when you accelerate or step on the throttle. The problem often means the air/fuel mixture is not being properly enriched or is going lean, or the ignition system is weak and is misfiring when the engine comes under load or the air/fuel mixture goes lean.
Possible causes: 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