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2005 CTS 2.8l: All six cylinders misfiring

22097 Views 11 Replies 7 Participants Last post by  Kingoftypos
I'm new here so I will try to be as detailed as possible.

1) One week ago the engine started to hesitate and briefly rumble when I accelerated. The CEL would flash briefly for 30 seconds and then nothing. Sometimes it wouldn't flash at all or hesitate and everything was fine.

2) The next day, I took it to an Advance Autoparts to have the codes checked and nothing showed up on their scanner

3) Today the CEL came on (no flashing) and stayed on and there is an intermittent rattle in the engine. Car starts fine with no hesitation but still hesitates on acceleration

4) Today I took it to Autozone and it was scanned again and it gave the following 7 codes

P0300- misfire detected random cylinders
P0301- misfire cylinder #1
P0302- misfire cylinder #2
P0303- misfire cylinder #3
P0304- misfire cylinder #4
P0305- misfire cylinder #5
P0306- misfire cylinder #6

5) Car is 2005 CTS 2.8L, 101,550 miles

I don't really know what to do next and the car's certified warranty recently expired and money is a problem. Thanks for your help.
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I don't know too much about engines but a good friend of mine does and is going to take a look at this for me. I'm having a similar problem with my 2006 cts 2.8. Only mine is 2 cyl misfire. He suggested I first change the spark plugs but because of the way the block is I would also have to change the intake manifold gasket. Hopefully that'll take care of the problem. I had to order the parts so I'm waiting for them to come in. The plugs cost me around $52 for platinum and the gasket kit was about $115.
^^^ thanks for the advice. Ill be sure to pass that on. Hopefully he wont have to change it out and I can recoup some of the money back. Between that and switching out my brake pads its proving to be a costly month in maintenance.
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