Engine Performance problem
2003 Chevy Suburban V8 Four Wheel Drive Automatic 80,000 miles
Suburban loses power when it reaches 30-35mph. When attempting to accelerate beyond 30-35mph, engine makes knocking noise. Bought vehicle used and did not have any problems at first. Started 7-8 weeks after purchase.
Knocking noise -could be the knock sensor not retarding the ignition timing. Also see 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)
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