As this forum gave me so much in learning about my vehicle, I thought I'd go ahead and give something back, and document my new found knowledge and show you the steps on how to change your 4.2L I-6 Spark Plugs.
Note: Common sense would dictate that you go ahead and do a throttle body cleaning in conjunction with the spark plug replacement; only 4 bolts and 2 connectors remain to remove the throttle body from the manifold, and the effort is well worth the time.
Tools Needed:
8 mm Socket
10 mm Socket
Regular Flat Blade Screwdriver (Optional)
3/8" Spark Plug Wrench
Socket Extensions
Supplies Needed:
Throttle Body and Carb Cleaner (CRC or Equivalent)
Shop Rags
Anti-Sieze Compound (Loctite or Equivalent)
Parts Needed:
6 AC-Delco Iridium (PN 41-103) Spark Plugs (As per AC Delco Service Bulletin, 103's are pregapped at manufacturer, and do not require gapping)
Instructions
Spark Plugs are accessed by removing the Resonator / Pre-Plenum (Marked Vortec 4200), located at the top of your engine.
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Begin by removing the Fuel Pressure Regulator Vacuum Line; slight twisting pressure will suffice.
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Then, remove the Air Box Hose Clamp, using an 8 mm socket, or optionally, a regular flat blade screwdriver.
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Next, remove the throttle body hose clamp, using the same socket or screwdriver.
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Remove the forward Resonator attach bolt, using a 10 mm socket.
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Followed by the aft Resonator attach bolt, with same 10 mm socket.
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After removing the wire loom clamp located just aft of the rear Resonator Attach bolt, you can now lift and remove the resonator; please notice the Crankcase vent hose under the Resonator attached to the valve cover; this just slides off.
You will now see the 6 coil packs exposed; Cylinders are numbered 1 through 6, with Cylinder 1 located at the radiator side, Cylinder 6 at the firewall side.
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Using a 10 mm socket, remove the single bolt attaching the coil pack.
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Using slight upward pressure while rocking side to side, pull the coil pack up and out of the spark plug well, and lay it to the side.
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You can now see the spark plug at the bottom of the well; using a 3/8 spark plug socket, remove and replace each of the 6 spark plugs. Before inserting the new spark plugs, apply anti-seize compound to the threads of the new plug; this will aid in removal during your next plug change.
[Note: you will need to move the wire loom that runs left to right over Cylinder 1 coil pack to access the bolt and remove the coil pack. I found the easiest way to do this is to remove the loom conduit cover, and pop / break the 3 plastic retaining clips that secure the conduit to the engine; clips are not needed, as the Resonator / Plenum when reattached holds the conduit securely]
Here’s a picture of the old spark plug (not to bad, considering they have about 180K Miles on them)
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In comparison, here’s what a new spark plug should look like:
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As noted; given you have the Resonator / Plenum already removed, you really should go ahead and clean your Throttle Body.
Instructions on cleaning our throttle body can be found here: http://forums.trailvoy.com/showthread.php?t=51619
Please note: it is easiest to do this with Cylinders 3 and 4 coil packs removed; it makes accessing the bottom throttle body bolts much easier.
Here is a picture of the manifold side of the throttle body pre-cleaning.
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Here’s a shot of the intake side of the TB pre-cleaning.
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Here’s the intake side of the TB after being cleaned.
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Just retrace your steps to reassemble; details to remember are to remember to reattach the Crankcase Vent hose under the Resonator, and don't forget your two connectors on your throttle body.
Hope this helps any of you contemplating doing the job yourself; with a quote of $130 to $180 from my local dealer to change plugs, I save myself close to $100 by doing it myself.
Note: Common sense would dictate that you go ahead and do a throttle body cleaning in conjunction with the spark plug replacement; only 4 bolts and 2 connectors remain to remove the throttle body from the manifold, and the effort is well worth the time.
Tools Needed:
8 mm Socket
10 mm Socket
Regular Flat Blade Screwdriver (Optional)
3/8" Spark Plug Wrench
Socket Extensions
Supplies Needed:
Throttle Body and Carb Cleaner (CRC or Equivalent)
Shop Rags
Anti-Sieze Compound (Loctite or Equivalent)
Parts Needed:
6 AC-Delco Iridium (PN 41-103) Spark Plugs (As per AC Delco Service Bulletin, 103's are pregapped at manufacturer, and do not require gapping)
Instructions
Spark Plugs are accessed by removing the Resonator / Pre-Plenum (Marked Vortec 4200), located at the top of your engine.
Begin by removing the Fuel Pressure Regulator Vacuum Line; slight twisting pressure will suffice.
Then, remove the Air Box Hose Clamp, using an 8 mm socket, or optionally, a regular flat blade screwdriver.
Next, remove the throttle body hose clamp, using the same socket or screwdriver.
Remove the forward Resonator attach bolt, using a 10 mm socket.
Followed by the aft Resonator attach bolt, with same 10 mm socket.
After removing the wire loom clamp located just aft of the rear Resonator Attach bolt, you can now lift and remove the resonator; please notice the Crankcase vent hose under the Resonator attached to the valve cover; this just slides off.
You will now see the 6 coil packs exposed; Cylinders are numbered 1 through 6, with Cylinder 1 located at the radiator side, Cylinder 6 at the firewall side.
Using a 10 mm socket, remove the single bolt attaching the coil pack.
Using slight upward pressure while rocking side to side, pull the coil pack up and out of the spark plug well, and lay it to the side.
You can now see the spark plug at the bottom of the well; using a 3/8 spark plug socket, remove and replace each of the 6 spark plugs. Before inserting the new spark plugs, apply anti-seize compound to the threads of the new plug; this will aid in removal during your next plug change.
[Note: you will need to move the wire loom that runs left to right over Cylinder 1 coil pack to access the bolt and remove the coil pack. I found the easiest way to do this is to remove the loom conduit cover, and pop / break the 3 plastic retaining clips that secure the conduit to the engine; clips are not needed, as the Resonator / Plenum when reattached holds the conduit securely]
Here’s a picture of the old spark plug (not to bad, considering they have about 180K Miles on them)
In comparison, here’s what a new spark plug should look like:
As noted; given you have the Resonator / Plenum already removed, you really should go ahead and clean your Throttle Body.
Instructions on cleaning our throttle body can be found here: http://forums.trailvoy.com/showthread.php?t=51619
Please note: it is easiest to do this with Cylinders 3 and 4 coil packs removed; it makes accessing the bottom throttle body bolts much easier.
Here is a picture of the manifold side of the throttle body pre-cleaning.
Here’s a shot of the intake side of the TB pre-cleaning.
Here’s the intake side of the TB after being cleaned.
Just retrace your steps to reassemble; details to remember are to remember to reattach the Crankcase Vent hose under the Resonator, and don't forget your two connectors on your throttle body.
Hope this helps any of you contemplating doing the job yourself; with a quote of $130 to $180 from my local dealer to change plugs, I save myself close to $100 by doing it myself.
is to alternate loosening and tightening in small increments until you think the bolt will come out easier. Loosen a little, tighten slightly and repeat. Sometimes it even helps on the initial loosen, if it feels like the plug isn't budging, just tighten a very slight amount.
