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2002 Chevy Malibu multipule misfires under load

Tiny
AUTOTECH3297
  • MEMBER
  • 2002 CHEVROLET MALIBU
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 10,655 MILES
Road tested car viewed data stream car has p0300 once car warms up and under load car misfires replaced plugs wires and fuel filter still same symptom. If you ease into it, it will be ok. Checked fuel pressue at idle 50-60 and also under load the same. Feels like a pluged cat but wont perform same symptom with car in park? Got any other answwers?
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Saturday, May 16th, 2009 AT 5:14 PM

6 Replies

Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
P0300 normally means vacuum leak or bad fuel

Engine misfiring can be caused by worn or fouled spark plugs, a weak spark (weak coil, bad spark plug wire), loss of compression, vacuum leaks, anything that causes an unusually lean fuel mixture (lean misfire), an EGR valve that is stuck open, dirty fuel injectors, low fuel pressure, or even bad fuel.
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Saturday, May 16th, 2009 AT 5:24 PM
Tiny
AUTOTECH3297
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  • 5 POSTS
As per your response I have repalced plugs wires and fuel filter. What do you think about a pluged cat. When car is in park or neutral car runs and accels great. But once you put in drive and accellerate poor accell and car jerks.
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Saturday, May 16th, 2009 AT 5:41 PM
Tiny
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Also fuel consuption way too much?
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Saturday, May 16th, 2009 AT 5:43 PM
Tiny
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  • MECHANIC
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Could also be the following 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
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Sunday, May 17th, 2009 AT 4:28 PM
Tiny
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Spent my sunday troubleshooting car found pluged cat symtoms were, excessive fuel usuage, engine temp immediately going up after about 2-3min. Once acceleration about 50mph engine will surge and accellerate
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Sunday, May 17th, 2009 AT 7:13 PM
Tiny
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You can determine if its clogged-up catalytic converter by using a vacuum gauge and pressure gauge
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Sunday, May 17th, 2009 AT 10:58 PM

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