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2019 Z71 Colorado
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Discussion Starter · #1 · (Edited)
All right fellow Z71 Owners and any other Colorado 2nd gen with a V6 3.6.
I have to say this is the most labor intense for me. I've work on many kinds of motors over the years. Simple thing as a "Tune-up" shouldn't be this Difficult, but it is...
Now I'm sure you know how to remove the plastic cover, 2 10mm bolts and loosen 3 8mm clamps and one quick release (tube in the front). Now for the fun removing the plugs, the drinker side is the easiest, driver side is well you have to remove the intake. There are 8 13mm bolts in the center, one of which is not easy to get too. It's the last one on the Caption side of the motor. To get to it you'll need a universal ext. slide it in from left to right in the hole, you'll have to feel for it. (There is a short video on YouTube but doesn't show much of the removal).
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Once you get it loosen, do the same 7 more times. Also, there is 10mm bolt on the driver side just behind the oil fill tube. (See first pic for reference)
You'll need to unclip the cruise control there are 2 plugs 1 is bigger you can squeeze with your fingers or pair of plyers. On the back it another tube with red lock, just push it up and pull off. Right side of pic below.
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Also, there are 2 10mm bolts one is pointed out here above. Best way to get to it is a 10mm on ratch wrench. That's what I used.
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Now the coil packs are bolted in with 10mm and the spark plug you'll need a deep well for the job.
On mine they forgot to use Anti-seize on the plugs. Thats not good for Aluminum. See lower pic.
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She is running a tad rich, and there some carbon buildup on them for only having 35k on them...
I have a bottle of Lucas fuel treatment, and on every fill-up will get about 6oz. What sucks is gas prices are going up and running anything higher than 87octaine is all I can do for now. (Yes, I used some Anti-seize on the new plugs). Note* the plugs are not 5/8 socket. It's a 14mm or 9/16 which can be found on Amazon or any good tool store.

I hope this helps others.
 

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2017 Chevy Colorado Z71 Extended Cab 4WD Summit White
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I have to do mine once the weather warms up... I have over 86K on mine at this point.
I totally agree changing spark plugs should not be as difficult as this set up
 

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Did I miss something? Why would you change plugs at 35K miles??
I'm curious about the valves too. That LGZ should be clean with it's built in "catch can" but I would love a look.
Any oil in the intake manifold?
Also, they look perfect to me. Rich?
 

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Man, it’s bad enough to have to do that job at 100,000 miles, I cannot see 35,000 miles.
 

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2021 Black \/6 4WD Z71 Crew Cab Short Box
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It’s early- but you never feel bad doing service early. If the original poster is like me they do a service when their butt twitches. Cheap day of garagery with warm fuzzy feeling when your done, and throughout the day if proper beer to work ratio was observed.
 

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2019 Z71 Colorado
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Discussion Starter · #9 ·
Did I miss something? Why would you change plugs at 35K miles??
I'm curious about the valves too. That LGZ should be clean with it's built in "catch can" but I would love a look.
Any oil in the intake manifold?
Also, they look perfect to me. Rich?
Hugh drop in fuel econ. Went from 19 down to 15/16 per. As for the Valves, It was Carbon up. No oil in the intake. With the amount of Carbon on the plug, to me seems a bit rich, but it is cold in Michigan.
 

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2019 Z71 Colorado
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Discussion Starter · #10 ·
I’m with @White016 on this. I get being “proactive” with maintenance but yikes. I probably wouldn’t wait right up to the 100,000 mile mark but those are basically brand new. Were you having problems that dictated a plug change?
Well, spark plugs were cheap at the moment. got them for under 8 bucks each. @ 100k no telling how hard they would be to get out then? They had 0 anti-seize. I'm going with KISS on the plugs. Have no codes on the computer. So going OLD SKOOL.
 

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IMHO there is no need to replace the sensor if there is not engine code.
I must have missed the section where you said you are doing this job at 35k.
I have about 42k and I was going to wait till at least 60k.
Going back to knock sensor, you are correct at 35k it doesn't make sense specially when you are not experiencing any issues. But I'm still curious how the valves looked, did you happen to look at them when you replaced the spark plugs?


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2019 Z71 Colorado
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Discussion Starter · #12 ·
I must have missed the section where you said you are doing this job at 35k.
I have about 42k and I was going to wait till at least 60k.
Going back to knock sensor, you are correct at 35k it doesn't make sense especially when you are not experiencing any issues. But I'm still curious how the valves looked, did you happen to look at them when you replaced the spark plugs?


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Couldn't see much, all was carbon up. (Looking in the intake channel). Can't see anything down in the spark plug tube. Unless I had a camera I could have looked.
 

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Discussion Starter · #15 · (Edited)
You should not use anti seize on spark plugs in an aluminum head. The anti seize will act as a lubricant during torquing and make you over torque your plugs which is very bad if you over torque just enough.
I take it you never had a seized plug. Well, it happen to me, so as for torque, I do it by the feel of hands, once tight, leave it. There are many who would agree with you. This has never failed me.
 

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Discussion Starter · #16 ·
Mine dropped from 24 to 22. I attribute that to the extremely cold temps as of late and probably the fuel blend also.

I'm not changing my plugs at 40k.

Yours look perfect.

Great write up too. Really didn't want to remove the intake.

$8 for plugs now. WOW.
I remember $1.
Yea, I didn't want to either, but the OCD in me when it comes to keeping my vehicles running top. Spark plugs are for today time under 8 bucks a plug for factory replacement wasn't that bad, as burring the same amount of fuel. I'm guess the "Winter fuel" mix is the issue. Did I waste my time? no, as I now have a base to work with... Yes, I remember 1.40-1.60 up to 2.50 plug when AKA longer lasting plug was the new thing.
 

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Heck, removing the intake manifold is about "normal" for a V6 engine now-a-days. 09 Ford Escape was quoted at $250 which I felt was 2 hours labor and parts. Found a video which helped a TON but it was easily 2 hours. There is ALWAYS 1 or 2 areas that are a bear and eat up more time than anything else!! :(

Like most things on vehicles I go by time and mileage. For the 100K stuff I generally do around 75K or 6ish years. Rational is that the next time you have to do(say another 75K) you are deciding to keep or trade the vehicle which directly corelates to doing the job again or not :) Plus even at 75K those plugs have been though a lot of heat cycles so they will be a bit tight...

P.S. Buddy's Toyota Highlander was a bear as engine was under the windshield cowl. 4 hours of labor there!!
 

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I take it you never had a seized plug. Well, it happen to me, so as for torque, I do it by the feel of hands, once tight, leave it. There are many who would agree with you. This has never failed me.
Same here, I use anti sieze on all spark plugs in aluminum heads, even on small engines.
 
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