Change Spark Plugs 05 Trailblazer

zip7111

Original poster
Member
Aug 10, 2020
16
Wisconsin
Hello,
Fairly new to this forum, lots of good info. I am not extremely handy when it comes to fixing things myself. I am considering changing the spark plugs as I have no idea how old they are. The car is an 05 with 145,000 and I have only owned it for about a year. How hard of a job is this to do? Is there anything I can royally screw up? Any input is appreciated.
Thanks,
Steve
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
Hey Steve, not too difficult of a job, just some stuff that needs to be removed. This video by our alumni @MAY03LT shows the process.

Chevy Trailblazer spark plug replacement 4.2 I6


One thing he doesn't mention is that it should be done on a cold engine as you are removing steel plugs from an aluminum block or risk galling the threads. Use only ACDelco 41-103 plugs as this engine is really finicky about plugs. If you don't have anti-seize, you can buy just a small packet of it at the parts store if you usually don't use this stuff a lot.

If while unscrewing the plugs you feel it's getting really difficult to turn, I recommend that you put everything back together and taking it to a shop. It doesn't happen often but on really old plugs they can be seized in there and forcing them will destroy the threads. It should be easy like in the video.
 

Ilikemy3s

Member
Dec 3, 2011
367
* Everyhing that Mooseman said is true. I changed my plugs on my 05 at about 200k.
* the side of my head is stamped with the warning to do when cold ( like oer night cold that is) and it even stated the torque setting to tighten them
* use even steady pressure on the ratchet to break them loose
* Do one at a time, working from front to back and mark them as to which cylander they came from as it will tell you about the bit of the condition.
* a little bit of oil in the plug well is normal but none is better. Just take note
* might be a good idea to replace coil packs as well as I did for peace of mind
* short extentions and swivels will be very useful. I had to make one for the #6 plug under the wiper cowl. That was the hardest and I had to climb into the engine bay.
*Take your time.
 
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zip7111

Original poster
Member
Aug 10, 2020
16
Wisconsin
In response to the post above. Is it really necessary to spend 300 bucks on coil packs if they seem to be fine? Will I notice any difference by replacing old packs with new ones?
 

Ilikemy3s

Member
Dec 3, 2011
367
In response to the post above. Is it really necessary to spend 300 bucks on coil packs if they seem to be fine? Will I notice any difference by replacing old packs with new ones?
at 200k on the odometer and had a coil pack fail just before the replacement, I figured to be better safe than sorry. Especially since I dive 80 miles a day just for work. and most of it is highway and I dont want to get stuck or have the truck run funny in the middle of no where.
 

Mektek

Member
May 2, 2017
656
FL
There are cheaper versions of the coils for a fraction of the ACdelco cost. I keep one in the truck as a spare. It can be changed in a parking lot if needed.
 

zip7111

Original poster
Member
Aug 10, 2020
16
Wisconsin
What brand of coil is the best bang for the buck? When I said 300.00 I was pricing mid grade options on RockAuto. The AC Delco packs were over 100 a piece.
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
Some guys have bought the cheap Amazon and eBay sets and haven't heard anything bad about them yet. These seem like a good deal at $70 + a 5% off coupon. Keep the old ones as spares.


Personally, I wouldn't replace them and just keep a spare or two in the glove box. When they fail is a total crapshoot but #4 fails first regularly because of water dripping on it from the firewall lip above.
 

Ilikemy3s

Member
Dec 3, 2011
367
I bought Delphi coil packs as they came recommended from two garages. Yeah a bit pricey but I like to have the peace of mind. Plus I am getting too old to want to change anything in a parking lot in bad weather. Oh .. when i did the plugs and packs, I also changed the air filter and the cleaned the throttle body at same time since everything was apart anyway. Truck has been running nice and smooth with no issues and I am not at 230k miles.
 

JerryIrons

Member
Dec 20, 2011
434
Is there anything I can royally screw up? Any input is appreciated.
Thanks,
Steve
Cold engine, as in overnight cool down. Use an air nozzle to clean up around the plug area before so no crap falls down in the hole once you remove the plug.

Once you crack a plug loose and start taking it out, if it seems to take a lot of effort to "unscrew", you can try the trick of tightening and loosening, repeat as you go until it feels loose like it wants to come out.

Little bit of antiseize on the threads, but none on the tip or going into the cylinder. And make sure when you start them in they don't go in crooked or cross threaded.

It's not that hard of a job, just be patient. you probably want to unplug the battery for 1/2 hour before you start it up so the computer learns how to run with new plugs. As was mentioned you will need a few extensions and maybe a swivel socket.
 

Mooseman

Moderator
Dec 4, 2011
25,262
Ottawa, ON
you probably want to unplug the battery for 1/2 hour before you start it up so the computer learns how to run with new plugs.
If you do that, you MUST clean the throttle body as all learned parameters for a dirty throttle body will be gone and it will idle like crap.
 

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