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`03 Trailblazer LTZ
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24 Posts
Discussion Starter · #41 ·
Awesome thanks! Going to work on it starting Thursday, I will post updates throughout
 

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2004 Trailblazer LS 4.20 L
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41 Posts
you could look in the oil fill and have someone crank it without starting it. pull the fuel pump relay or fuse. sometimes you can see in there some people can tell just by listening if a valve stuck. another trick is seafoam in the crank case to clean the gunk out. have you checked the manifold bolts? been awhile i dont remember but those can come loose and raise hell, too. if the lights not on, maybe a little seafoam will break it loose for ya. best of luck
 

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`03 Trailblazer LTZ
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Discussion Starter · #43 ·
Ok guys I’ve got the valve cover open and inspected the camshaft, lifters, springs, everything I might have found the problem, although I’m not really sure.

i think I have a bad roller(?) on the exhaust side camshaft. When comparing both on cylinder 5 I noticed that one of them seems to be more round, which would cause the valve not to be lifted. I’m trying to measure it somehow. I‘m not sure if my eyes fault me, but it seems like it.
Can‘t really see it on a picture
 

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`03 Trailblazer LTZ
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Discussion Starter · #44 ·
Ok so I wasn’t able to measure it properly. It could have just been that the angle I was looking at it made it seem more round. The whole area looked clean, not much if any gunk or dirt or whatever was visible.
I’ve put in new gaskets and put everything back together. Also put in ac Delco plugs just in case (had autolite before).
Of course nothing has changed. Problem still there
 

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`03 Trailblazer LTZ
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Discussion Starter · #45 ·
Ok so yesterday I drove about 100 miles on the highway and in the city, different speeds and rpm.
I noticed the misfire while idling at stop lights. I didn´t have a loss of power on the highway though, which made me think.

Is there a way to have a misfire ONLY at idle?
 

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2004 Trailblazer LS 4.20 L
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41 Posts
you may have a little vaccuum leak or a spark plug boot that just isnt quite touching but it really sounds like it must be a bummed out wire or connection. when its at speed the vibration is different than at idle. its higher frequency, loose wires do that kind of stuff. probably an injector if its not a coil. so, one of those wires or circuits or a vaccuum leak. its all i got. if the SES light isn't on steady, probably not bad enough to track down or worry about. im going to give it some deep thought maybe think of something else. that elbow for the PCV is known to crack. could be a bad pin on the PCM even. good luck brother!
 

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2004 Trailblazer LS 4.20 L
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were the spark plugs black by any chance? any fuel in the vacuum lines?
 
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