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2004 Chev Silverado

Tiny
GARY GEORGE
  • MEMBER
  • 2004 CHEVROLET SILVERADO
  • V8
  • 4WD
  • AUTOMATIC
  • 122,000 MILES
I have a 2004 chevrolet silverado 1500 5.3 liter automatic. The check engine light came on and the truck engine started to idle rough like it wanted to die but didnt. It not only does this in gear but also in park. I had 3 different diagnostic test done only to recieve multiple codes of things that could be the problem, such as, oxygen sensor, lean fuel, engine vacume leak or misfire, low fuel pressure, power train module, computor has recognized a rich or lean condition on the left bank only probable cause, mass air flow sensor. Those are from Auto Zone diognostic reading. Car MD diognostic readings are anywhere from plugs n wires wich ive allready replaced to intake manifold gaskets, crankshaft positioning sensor. Since this problem ive noticed a drop in power and fuel economy. Can anyone help me out to better pinpoint the problem with out replacing a bunch of parts that dont need to be replaced? P.S. The truck has aaproximatley 122,000 miles on it.
Thanks, Gary
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Friday, February 11th, 2011 AT 12:35 AM

8 Replies

Tiny
WRENCHTECH
  • MECHANIC
  • 20,761 POSTS
Clear all the codes and start over. After the check engine light comes on again, have the codes read and post the exact numbers here.
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Friday, February 11th, 2011 AT 1:02 AM
Tiny
CARADIODOC
  • MECHANIC
  • 33,874 POSTS
Check with your local auto parts stores to see if they have a smoke machine you can rent or borrow. That will let you force white smoke through a vacuum hose at 2 psi. Then you watch to see where it comes out. Intake manifold side gaskets are a common source on GM V-type engines but coolant leaks are more common.

The crankshaft sensor will cause a stalling or no-start problem. Most of the symptoms you mentioned could be attributed to a vacuum leak. Any "unmetered" air that gets in without going through the mass airflow sensor will result in unburned oxygen in the exhaust where it will be detected by the oxygen sensors. That will direct the Engine Computer to add more fuel to the mixture. No matter how much fuel is added, there will always be that extra air.

The same thing can happen from an exhaust leak ahead of the catalytic converter. Between the pulses of exhaust gas, the momentum creates pulses of vacuum that draws air in through the leak. That air gets detected as a lean condition on one side of the engine.

Caradiodoc
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+1
Friday, February 11th, 2011 AT 1:08 AM
Tiny
WRENCHTECH
  • MECHANIC
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I'm not so sure there aren't some false codes mixed in there from things being unplugged and messed with. I would start over first to make sure your not searching for something that isn't even there.
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Friday, February 11th, 2011 AT 1:12 AM
Tiny
GARY GEORGE
  • MEMBER
  • 12 POSTS
Thank you very much for your quick reply! Your information was very helpful. However I did forget to add somthing else. Often after I start my truck or have been driving it I can smell antifreeze when I walk by the front drivers side wheel. Ive looked for leaks and cannot find any or havent noticed any puddling under the truck or wetness under the hood anywhere. Do you think this could be attributed the the way the truck is running or a blown intake gasket?
Thank You again, Gary
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Friday, February 11th, 2011 AT 1:38 AM
Tiny
GARY GEORGE
  • MEMBER
  • 12 POSTS
Replying to wrenchtec. Ive cleared out the engine light and the truck ran just fine for about 30 miles or more. When it came back on I stoped the vehicle and shut it off plugged in the Car MD diagnostic. I turned on the ignition switch and this is he code that it came up with, P0300.
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Friday, February 11th, 2011 AT 2:13 PM
Tiny
WRENCHTECH
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That's a pretty generic misfire code that really doesn't help us too much. I would run it a little longer and see if anything more specific sets.
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Friday, February 11th, 2011 AT 2:22 PM
Tiny
GARY GEORGE
  • MEMBER
  • 12 POSTS
Reply to wrenchtec, I checked the spark plugs and no difference between any of them. However after backing the truck in the garage it started to run rough again. After I got out of the truck I noticed a rotten egg smell comming from the exhaust. Could this be pluged converters?
Thank you, Gary
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Friday, February 11th, 2011 AT 6:26 PM
Tiny
WRENCHTECH
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  • 20,761 POSTS
Closing out question
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Friday, March 11th, 2011 AT 4:37 PM

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