Join Date: Nov 2009
Location: Baker River Valley, NH
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Notice the 1 & 6 plugs are not exhibiting ground or spark electrode erosion and appear to have a disc bonded to the ground electrode. New plugs will have this disc in place.
Plugs 3 & 5 have significant ground terminal erosion and no disc. Someone might've attempted to gap the plugs and dislodged the disc.
Plug 2 has spark electrode erosion and corresponding wide gap. Not sure what happened here... time and miles likely.
Looks like you've simply reached the end of the useful service life on your spark plugs.
Get six AC Delco 41-110 Iridium spark plugs and install them. Or six 41-962 Platinum... I believe the 08 came with Iridium spark plugs. Don't overthink things... Use the same spark plug metal type that your engine came with from GM. Iridium causes spark issues in the T400 trucks and the Gen III LS motors in the T800 trucks.
DO NOT GAP the plugs. They are factory gapped... the iridium or platinum disc can separate if you monkey with the ground electrode.
Get either Delphi XS10544 or Denso 6716258 wire sets for your 3.5L. AC Delco wires are made in China now. Delphi and Denso actually still make a quality product and Delphi is likely what she was wearing when she rolled off the line.
Wipe a dab of non-conductive silicone Di-electric grease inside the end of the coil and plug wire boots.
I usually put a thin layer of never seize in just the plug threads with a plumbers acid brush. This is very conductive so you absolutely do not want to get this on the ceramic or the not-threaded metal bits so be careful with it.
2009 Impala SS
"Speed never killed anyone. Suddenly becoming stationary... that's what gets you." Jeremy Clarkson
Last edited by hatzie; 06-08-2019 at 12:13 PM.