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?
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.
Was this
answer
helpful?
Yes
No
Saturday, May 16th, 2009 AT 5:24 PM
Tiny
AUTOTECH3297
  • MEMBER
  • 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.
Was this
answer
helpful?
Yes
No
Saturday, May 16th, 2009 AT 5:41 PM
Tiny
AUTOTECH3297
  • MEMBER
  • 5 POSTS
Also fuel consuption way too much?
Was this
answer
helpful?
Yes
No
+1
Saturday, May 16th, 2009 AT 5:43 PM
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
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
Was this
answer
helpful?
Yes
No
Sunday, May 17th, 2009 AT 4:28 PM
Tiny
AUTOTECH3297
  • MEMBER
  • 5 POSTS
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
Was this
answer
helpful?
Yes
No
Sunday, May 17th, 2009 AT 7:13 PM
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
You can determine if its clogged-up catalytic converter by using a vacuum gauge and pressure gauge
Was this
answer
helpful?
Yes
No
Sunday, May 17th, 2009 AT 10:58 PM

Please login or register to post a reply.

Related Engine Misfire Content

Intermittent Misfire
VIDEO
Intermittent Misfire
Instructional repair video
Misfire Random Code P0300
GUIDE
Misfire Random Code P0300
The world of automotive diagnostics can be complex, with numerous codes and potential issues to keep track of. One of the more common engine diagnostic codes is P0300, which...
VIEW MORE