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2005 Buick Century random misfire

Tiny
JUSTIN U
  • MEMBER
  • 2005 BUICK CENTURY
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 65,000 MILES
I have a 2005 Bucik Century that is very hard to start and is running extremely rough. I can the codes and found code po300 for random misfire. I have checked the plugs and wires and dont see anything out of the ordinary. I am looking for a little help with the diagnosing of this. Any Ideas?
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Saturday, January 3rd, 2009 AT 12:02 PM

11 Replies

Tiny
BRIAN 1
  • MECHANIC
  • 1,030 POSTS
Remove each sparkplug wire from each coil pack and see if the towers on the coilpacks are rusty or burnt, very common problem. Post back with what you find and will advise from there.
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Saturday, January 3rd, 2009 AT 1:28 PM
Tiny
JUSTIN U
  • MEMBER
  • 9 POSTS
I have already had the wires off the coil pack and didnt see any rust or corrosion of any kind
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Saturday, January 3rd, 2009 AT 1:31 PM
Tiny
BRIAN 1
  • MECHANIC
  • 1,030 POSTS
You will need a scan tool to find out which cylinder or cylinders are missfiring, this could be fuel related or spark related or mechanical. It's very hard to say what it is with out some sort of testing. Try and find out if it's spark or fuel. Post back with any other questions.
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Saturday, January 3rd, 2009 AT 1:41 PM
Tiny
JUSTIN U
  • MEMBER
  • 9 POSTS
I have been told that the egr valve could cause this. Is that possible'
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Saturday, January 3rd, 2009 AT 1:45 PM
Tiny
BRIAN 1
  • MECHANIC
  • 1,030 POSTS
It could, but this missfires all the time if it was the egr there would be an egr code and if it was the egr when the car was cold it would run fine until it got warm and the egr started to operate then it would run rough.
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Saturday, January 3rd, 2009 AT 1:51 PM
Tiny
JUSTIN U
  • MEMBER
  • 9 POSTS
Ya thats true. Im not really sure what is goin on with this thing it just started missing all of the sudden and will not start without excessive cranking and pumping the pedal which to me seems crazy. But I may have to get my hand on a better scanner
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Saturday, January 3rd, 2009 AT 1:56 PM
Tiny
BRIAN 1
  • MECHANIC
  • 1,030 POSTS
If you have to pump the pedal to start thats a fuel problem. Check the fuel pressure with a guage and post back.
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Saturday, January 3rd, 2009 AT 3:05 PM
Tiny
JUSTIN U
  • MEMBER
  • 9 POSTS
I got outside just in time to see my dad trying to get it running with starting fluid. (Scared the crap out of me) but it still wouldnt start
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Saturday, January 3rd, 2009 AT 3:47 PM
Tiny
BRIAN 1
  • MECHANIC
  • 1,030 POSTS
What do you mean, did it start with starting fluid or it just wont start? I need you to check fuel pressure, we need to start somewhere.
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Saturday, January 3rd, 2009 AT 6:46 PM
Tiny
JUSTIN U
  • MEMBER
  • 9 POSTS
I have realized that it will start and run on its own when it is cold but once the engine heats up it starts to miss and then will die. They checked the fuel pressure today and said that it was normal
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Sunday, January 4th, 2009 AT 6:52 PM
Tiny
BRIAN 1
  • MECHANIC
  • 1,030 POSTS
Then we need to check spark, take some soapy water in a spray bottle and spray the wires while its running and see if there are any sparks, to check for a bad wire also pull some plugs and see if any are cracked or have carbon tracking. It's very hard to help when we dont know what cylinder or cylinders are missfiring, this could still be fuel or spark problem. Could be a bad injector, bad wire, bad coil pack, bad plug, etc. Post back with what you find.
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Monday, January 5th, 2009 AT 9:59 AM

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