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2005
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Discussion Starter · #1 ·
2005 GTO running rough, diagnostic codes misfire.. #6 I believe. Changed the plugs and wires, while doing that noticed the coolant temp sensor had a bad connection due to the rubber end that is around the prongs was broke off. Anyway, changed that as well. Start it up. Ran down the street and. Had to turn around. Very sluggish and starts missing like it isn't getting enough fuel somewhere around 35 mph.. car goes into safety mode. Get home not ever getting out of 3rd gear. She vibrates horribly at idle and just about dies but idling about 8-9 rpm, just very rough. I would like to have some advice before spending any outrageous amount of money.... help!
 

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898 Posts
You could try removing the neg battery cable for about 5 minutes to get the computer reset. Also, are there any other diagnostic codes showing up?

Larry
 

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2005
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5 Posts
Discussion Starter · #3 ·
You could try removing the neg battery cable for about 5 minutes to get the computer reset. Also, are there any other diagnostic codes showing up?

Larry
I will try resetting the computer after work. The codes before the plug and wire change were
P0300
P0455
P0300P
P
You could try removing the neg battery cable for about 5 minutes to get the computer reset. Also, are there any other diagnostic codes showing up?

Larry
I will definitely try resetting the computer! Thank you! And the codes before plugs and wires changed were
P0300
P0455
P0300P
P0455P
And after...
P0068
P0300
P0106P
P0300P
 

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Just a complete shot in the dark as I don’t yet own a GTO, and I’m not familiar with the codes you’ve posted, but my wife’s last vehicle was an 05 Cadillac Escalade with the 6.0L and it did what you’re describing in terms of symptoms a couple of years ago, and after replacing plugs/coils we determined that there was actually a problem with a fuel injector.

It would cause a misfire that would get significantly worse around 35-40mph, and was allowing raw fuel to feed into the cats which resulted in those having to be replaced when we fixed everything else. We decided to retire the beast when the problem returned about a year after we fixed it the first time.

I could be way off base here, but since this forum doesn’t seem to get a lot of traffic, and the problem you describe sounds so similar to what we experienced, I figure it might be worth mentioning. I’m not sure how different the 6.0 in the Cadillac might be from the one in the GTO, but it’s an idea nonetheless.
 

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2005 GTO 6 speed Manual
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5 Posts
Process of elimination it could be the injector. I always run sea foam through my fuel system and I put it in the crank case. Run it to operating temperature then change the oil.
 
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