2002 Chevy Impala hesitation

2002 CHEVROLET IMPALA
13,000 MILES • 4 CYL • FWD • AUTOMATIC
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MBRADLEY
  • MEMBER
  • 1 POST
my check engine light came on, and i took it to be put on diagnostic machine and it pulled up front oxygen sensor code. the car was already hesitating a little when i first get in it to drive off in the morning, but the hesitating got worse after i took it to have the oxygen sensor changed. the converter was checked and cleaned. it slows down and speeds up again and again and have black smoke coming from the exhaust and a smell. they told me it was in my fuel line, i dont know what to do. its like they made things worse after changing the oxygen sensor. I only had the car a year and haven't had it tuned up. just changed the oil every 3,000 miles.
May 26, 2009 at 8:53 PM
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RASMATAZ
  • CAR REPAIR CONTRIBUTOR
  • 75,992 POSTS
Possible Causes of Engine Hesitating or Stumbling

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
May 27, 2009 at 4:10 AM
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