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2005 chevy trailblazer_ls
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28 Posts
Discussion Starter #1
New 05 Trailblazer LS w/ 4.2 I6 owner.
The check engine light is on, ran code reader, came out as something to do with thermostat. Not too worried about that since it doesn't appear to be running hot, looked up OEM thermostat temp as 190, gauge is reading about 200.

What I am wondering about though is I have noticed a slight ticking noise under acceleration. It goes away almost instantly when I start coasting though. Sounds like it's coming from engine compartment but I can't think of anything that would tick only under accelerating and not all the time. I don't exactly have the lightest right foot around if that could cause it.
Any ideas what could be causing this? It's not overly loud, can really only hear it with windows up and radio off.
 

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2002 chevy trailblazer_ltz
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2,762 Posts
I would change stat very soon.they fail open and it takes much longer to heat up causing extra gas which gives you bad gas mileage and dumps to much gas and destroys your Cat.as for the tick,it could be the usual cracked manifold or sticky valves.
 

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2005 chevy trailblazer_ls
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28 Posts
Discussion Starter #3
I would change stat very soon.they fail open and it takes much longer to heat up causing extra gas which gives you bad gas mileage and dumps to much gas and destroys your Cat.as for the tick,it could be the usual cracked manifold or sticky valves.
Doesn't seem to be heating up slow, usually up to normal operating temp in under 2 miles, then will stay right about 200-215 indefinitely depending on ambient air temp... And I'm doing work to it this weekend, so I'll check and hope it's a cracked manifold.
 

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2008 chevy trailblazer_lt
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72 Posts
My last TB had an annoying tick/rattle only under acceleration as well. I looked for months to find out what it was only to find it was the prop rod vibrating. I took the mount off and moved it (the piece that the rod snaps into when not in use) 1/2" and as some would say, bob was my uncle. With mine I could really hear it in the cabin, not so much outside but it annoyed the **** out of me for months and made me feel like a tool when I saw it was the stupid prop rod.
 

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2005 chevy trailblazer_ls
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28 Posts
Discussion Starter #5
I'm actually thinking it's more in line with sticking valve now that that was mentioned because I have started to feel vibration when stuck at a long light and when I stood by tailpipe tonight it sounded rough, not a smooth hum.
But I'll check to make sure rod is tight.
 

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2005 chevy trailblazer_ls
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28 Posts
Discussion Starter #6
Got home tonight and pulled into garage and let it idle for a minute, could hear the idle rapidly going up and down. Beginning to regret buyin this thing, at least I got it for about 1100 under kbb value. :cool:
 

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2003 chevy trailblazer_lt
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Got home tonight and pulled into garage and let it idle for a minute, could hear the idle rapidly going up and down. Beginning to regret buyin this thing, at least I got it for about 1100 under kbb value. :cool:
Check out the threads on cleaning the throttle body. It works, after cleaning the idle will smooth out and idle at 600 rpm's.
 

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2005 chevy trailblazer_ls
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28 Posts
Discussion Starter #8
Well looks like add throttle body cleaning to list of things to do this weekend.
 

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2005 chevy trailblazer_ls
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Discussion Starter #10
Could I just use plain old carb cleaner? All the threads I saw said throttle body cleaner, but never mentioned if carb cleaner will work or not. I'm guessing it'd work the same but might as well be safe and ask.
 

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2005 chevy trailblazer_ls
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28 Posts
Discussion Starter #12
Well discovered some relatively good news tonight... The funky idle is just in my head I guess. Changed serp belt and listened both under the hood and at tailpipe while it was seating the belt, and didn't hear any variation in rpm.. Probably just thought I heard it because the car I replaced with TB had done that for over a year.
 

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2005 chevy trailblazer_ls
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28 Posts
Discussion Starter #13
Changed rear diff fluid today. Come to find out my TB is actually an LS EXT. Not just an LS like I had thought. So the half hour job of changing fluid turned into a 4 hour one running around because nobody had the cover gasket in stock, and when I finally found one it was 40 bucks!! :mad: :hissy: :mad:
Big jump from 10 bucks for plain LS to 40 for EXT...
 

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2005 chevy trailblazer_ls
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28 Posts
Discussion Starter #14
Just for future reference if anybody else asks if carb and throttle body cleaner are interchangeable... You CAN use carb cleaner on throttle bodies but NOT tb cleaner on carbs.

They have essentially the same ingredients, just different FORMS of them, and throttle body cleaner has some type of oil in it to help deter the crap from crank case from sticking again, and carb cleaner doesn't have that.
 

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2005 chevy trailblazer_ls_ext
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18 Posts
I just got done doing mine about a week ago and it is just fine. I used regular carberator cleaner.
 

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2003 gmc envoy_slt_xl
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Same problem

I have been having the same ticking sound under acceleration for the last 2-3 years and it hasn't affected the driveability or the gas mileage. Not sure what it is but I've been living with it and just keeping an eye on it to see if it gets worse. My truck is an 03 Envoy SLT EXT with about 145,000 miles on it. I've tried higher octane gas, cleaned the throttle body and changed the stat with no change. If anyone finds out what's causing it let me know.
 
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