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Discussion Starter #1
Hi, I am new to the site. I just got back from Iraq in april and I bought a 2002 Trailblazer LS 4x4 a couple days after I bought it I noticed a knocking sound comeing from the engine. I dont know if it was there before I bought it or if it just started but that is when I noticed it. When I first start the engine you can hear it louder and it softens up some after it is warmed up but never goes away. When going down the highway I cant hear it unless I am stopped. That has been about 4 months ago and I have put about 7000 miles on it and that included about 8 trips that were 600 miles or longer. I have been able to pull a 6 x 12 Uhaul trailer loaded with furnature and a bass boat with no problems. I took it to a dealership and they could not figure out what the sound was without breaking down the engine and I would not let them do that because I didnt have the money. They did tell me that it sounded like it was coming from the lower half of the engine. Can anyone help me out?
 

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2004 chevy trailblazer_lt
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43 Posts
Ticking Sound

I had a ticking sound thought it was the fan clutch, replaced clutch no change. Also had a hesitation on acceleration around 2K RPM going up hill. It ended up being the transmission which went out. Rebuilt transmission and no more ticking. Check transmission, burnt fluid or metal shavings in fluid maybe an indication.
 

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2005 chevy trailblazer_ls_ext
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Hi, I am new to the site. I just got back from Iraq in april and I bought a 2002 Trailblazer LS 4x4 a couple days after I bought it I noticed a knocking sound comeing from the engine. I dont know if it was there before I bought it or if it just started but that is when I noticed it. When I first start the engine you can hear it louder and it softens up some after it is warmed up but never goes away. When going down the highway I cant hear it unless I am stopped. That has been about 4 months ago and I have put about 7000 miles on it and that included about 8 trips that were 600 miles or longer. I have been able to pull a 6 x 12 Uhaul trailer loaded with furnature and a bass boat with no problems. I took it to a dealership and they could not figure out what the sound was without breaking down the engine and I would not let them do that because I didnt have the money. They did tell me that it sounded like it was coming from the lower half of the engine. Can anyone help me out?
That is pretty common with many of the I6 engines. I believe it is called "cold carbon knock". Some recommend using Seafoam (I've never used it) or try running Techron fuel injector cleaner for a few tankfuls. Also use a "top tier gasoline" if it is available in your area.
http://www.toptiergas.com/retailers.html
 

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2002 olds bravada
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That is pretty common with many of the I6 engines. I believe it is called "cold carbon knock". Some recommend using Seafoam (I've never used it) or try running Techron fuel injector cleaner for a few tankfuls. Also use a "top tier gasoline" if it is available in your area.
http://www.toptiergas.com/retailers.html
:iagree: it is cold-carbon knock...but he states that it doesn't go away. it only gets quieter, but never goes away. hmm try using a bottle or 2 of techron. it helps with the noise. i've also heard that changing to synthetic oil helps a lot too..
 

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Western Canada Chapter
2003
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6,411 Posts
Check to see if your VIN# falls in this category.

2002
Chevrolet
TrailBlazer - 22100007 to 22358861

The sticky on the header of this category talks about the cylinder bore liner cracking and causing problems.

There is a special policy coverage to 100,00 miles or 7 years. Check out the thread.
http://forums.trailvoy.com/showthread.php?t=427
 

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Discussion Starter #6
I just talked to a chevy dealer on the phone and here is the situation I am in. I can take my TB into the dealership to have them check it out to see if I have the problem, but it could or could not be the problem that is covered. If it is the problem then chevy will pay for everything that has to be done. If it is not the problem then I have to pay for it. but they wont be able to tell what is the problem unless they remove the head and look. I will have to pay for the head removal if it is not the problem, I dont have to pay for it if it is the problem. so here are my options, I can try to deal with the problem and hope that it never leaves me stranded anywhere, or I can take it into the shop and hope that they pay for the problem. I am running out of time because soon the recall will be invalad because of time.

Here is more detail about what is going on.

I have a 2002 Trailblazer 4x4, at startup there is a loud knocking sound that speeds up when the engine is being reved up. After the engine warms up the sound dies down but it can still be heard. the truck died on me once about a month back, I started it and when I put it into Drive it died, then it started up fine after that and I have not had a problem with it dieing since. I have had the vehicle since April. I have driven from Kansas to Arkansas, then Arkansas to Kansas pulling a 6 x 12 Uhaul. I drove back to arkansas then I drove it to GA from arkansas 2 times. the first time pulling a 5 x 8 Uhaul and the second time pulling a 15' Bass boat. I have not had any problems with performance. My fuel economy was about 8 MPG on one of my trips when I was pulling the 5 x 8 uhaul but I did a basic tune up and that fixed that problem. I normally get about 15 to 18 MPG.

Should I take it into the shop and take the chance that it is not a serious problem or should I deal with it and hope it never blows up?
 

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Premium Member
2007 chevy trailblazer_ss_1ss
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1,852 Posts
Could be carbon knock, or it could be a rod knock. If it is a carbon knock and it isn't too bad, a BG Induction Service could take care of it. One of the guy's at work was working on his parent's Saturn with a 1.9L and everyone thought it was a really bad carbon knock, he used a ton of BG chemicals and other tricks and it wouldn't fit it. He pulled the oil pan and it had spun a rod bearing. You can try some cleaning stuff, but if it won't help they'll definately have to tear down the engine to find the problem.
 

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2003 chevy trailblazer_ls
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Id try seafoam/techron 1st.... if it doesnt go away or quiet down.. then proceed with dealer.
 

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Discussion Starter #9
If I were to somehow record the sound and post it somehow, is there anyone that would be able to tell the difference? because with cold carbon knock I heard that it completely goes away after your engine warms up but mine never goes away it just softens.
 

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Hi, I am new to the site. I just got back from Iraq in april and I bought a 2002 Trailblazer LS 4x4 a couple days after I bought it I noticed a knocking sound comeing from the engine. I dont know if it was there before I bought it or if it just started but that is when I noticed it. When I first start the engine you can hear it louder and it softens up some after it is warmed up but never goes away. When going down the highway I cant hear it unless I am stopped. That has been about 4 months ago and I have put about 7000 miles on it and that included about 8 trips that were 600 miles or longer. I have been able to pull a 6 x 12 Uhaul trailer loaded with furnature and a bass boat with no problems. I took it to a dealership and they could not figure out what the sound was without breaking down the engine and I would not let them do that because I didnt have the money. They did tell me that it sounded like it was coming from the lower half of the engine. Can anyone help me out?
I have the same problem with my 03 Chevy trailblazer my son owned it before me he never maintained it before I got it I put Lucus oil treatment and it quieted it down complete oil change and now use the better octane gas changed the spark plugs which was really easy for me as a woman by a you tube video car runs way better and the sound it much more quieter was told by many people that it’s something in the lower part of the engine but the cost is probably not worth fixing I just keep up regular maintenance check fluids often but keeping my eyes out if any one really knows what the noise is. Seems like every vehicle has faulty patterns looks like knocks for Chevy trailblazer
 
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