Hey Every Body
I am new to the forum and wanted to share with everyone a guide w/ images I just got done putting together with step by step directions, tools needed, and typically over looked details that a first timer changing their plugs on there Trailblazer / Envoy should know.
I have it here as web based Google Doc Version.
The text based version is below. Message me if you'd like the PDF version, you can also download the guide from the Google Docs Link above.
Be on the look out for my Step by Step guide to changing out the fuel sending unit in the next few weeks!
How to change the spark plugs on a 2005 Chevy Trailblazer 4.2L I6
Step by Step Guide
Tools / Items Needed:
Flat head Screw driver
5/8 Spark Plug socket
1 6 or 9 Socket Extension
1 3 Socket Extension
10mm open ended wrench
Breaker bar or metal pipe (for leverage on the end of the socket wrench; used on the 6th spark plug just under the firewall, this one is a knuckle breaker, disregard if you have a long handled socket wrench)
6 pack of beer or fresh pack of cigarettes (Ether of these are an essential tools if you partake)
6 ACDelco 41-103 Iridium Spark plugs or preferred brand(ACDelco Spark plugs come pre-gapped from the factory at .043 but double check to make sure they are correct and did not change during shipping)
Anti-seize compound (Not a requirement put good to apply to the threads of the spark plug for the next guy who may have to change out the plugs)
Remove the Air Resonator by undoing 2 - 10mm bolts on the left hand side, loosening the clamp around the air intake tube to the right of the mass air flow sensor, and the clamp where the air resonator joins the throttle body. Be sure to detach the mass air flow sensor wire from the resonator by undoing the plastic clip.
Now that you have removed the air resonators you have exposed the top of the coil packs of the 4.2L Inline 6 Engine. Each coil pack is held down by a 10mm bolt. I choose to start one spark plug at a time and work my way from plug 6 (under the firewall) and forward.
With the 10mm socket loosen the bolt which holds the coil pack in place. No need to disconnect the wire there is plenty of play to pull the coil pack up and set it to the side.
Plug 6 is the hardest one due to lack of maneuverability; this is where the breaker bar or pipe comes in handy to loosen the tightness of the plug. Once it is lose you can put the bar or pipe to the side it should not be needed for the rest of the rest of the plugs.
With the 5/8s spark socket on the end of ether a 9 extension or a 6 & 3 Extension remove the plug. Make sure nothing falls into the hole. Now take your new spark plugs and insert it into the end of the 5/8 spark plug socket, should you choose; apply a thin bead of anti-seize to the spark plug threads. Insert the spark plug into the hole and start to tighten by hand to be sure you do not cross thread. Tighten the plug; be sure not to over tighten for fear of snapping the plug off, use your best judgment. Not reinsert the coil pack being sure the it is properly seated, and tighten the bolt back down.
Repeat above for plugs 6 through 2. Plug 1, closest to the front requires special attention see next step.
Plug 1 is not too hard to remove but does require special directions because there is a plastic wire channel/guard which runs across it. Undo the bolt using the 10mm open ended wrench. Once the bolt is loosened slightly pull up on the coil pack, rotate about 90 degrees to the left while at the same time slightly tilting at a 45 degree angel towards the wind shield to remove the coil pack and clear the wire channel / guard. Now return to step 3 direction when it comes to changing out the spark plug.
Now resemble. Be sure to tight the air intake tube clamp on the right, and left where the resonator connects to the throttle body. Tighten down the 2 bolts which hold down the air resonator; dont forget to re-clip the mass airflow sensor wire just behind bolt 2 on the resonator.
Note: Be sure to check the tube which connects from the air resonator into the engine. This tube is located under the resonator on the left in line with plug 1.
Thats it! You are all done! Now drink a beer, smoke a cigarette, or take your girl out for a ride. Enjoy the regained power youll get in your Trailblazer or Envoy.
My last note here: GM/Chevy say the stock plugs are good for up to 100k miles; however I have found in my truck and my friends that they tend to show sign it is time for a change between 75k -90k on average. When I removed my plugs at 88k they were way gone(I do a lot of long distance travel for work and drive hard), hell the average gap on the plugs was between.051-.054 ; the plugs showed signs of bridging and were blackened. My fuel economy sucked 12-14 mpg and the truck ran like crap. Now I got the mpg back up to between 18-20 mpg, I changed my oil, new tires, and truck runs great again!