Welp, more bad news. The back tap barely engaged - took such little pressure to turn that hardly felt anything while turning it out. I'm not even sure it actually caught the threads - felt almost like spinning freely in air during each pass.
I'd had a suspicion the new plug was falling through and just resting on the crush washer while I was trying to screw it in. I tried a different plug from the same new set (fit perfectly in another cylinder) which didn't catch either. Denso SK20R11, which happens to match all 8 old plugs that came out. I used my sparkplug extension to mark depth on the bad one and a good one that was already torqued down. Depth in #4 (fully bedded in plug) was identical to #6 (the problematic, not-yet-threaded plug).
So I'm about certain the threads are blown out. Could've been the plug walking/blowing out - but the threads look good/clean enough (even before any work) that I'm wondering if this cylinder was tapped/enlarged at some point by the small town auto shop the PO used.
Eerily similar to this thread about a 2UZ in a '99 100 Series (even down to cylinder 6) except that the plug I removed doesn't have any evidence of an insert. Maybe the insert came out two plug changes ago? I dunno but at this point I may mess around and buy a Sav-a-Thread to see if it screws right in without any more cutting. Thoughts?
My next option: Time-Sert 4412e-111. It's out for delivery today so prep starts now: clean/vacuum the cylinder, turn the motor to ensure valves are closed, upgrade my janky air hose vacuum attachment to fit the big shopvac, re-watch some installs on Youtube.
Sorry to sidetrack the thread but at least we're back to the main topic of more drastic thread repair methods. Wish me luck!
I'd had a suspicion the new plug was falling through and just resting on the crush washer while I was trying to screw it in. I tried a different plug from the same new set (fit perfectly in another cylinder) which didn't catch either. Denso SK20R11, which happens to match all 8 old plugs that came out. I used my sparkplug extension to mark depth on the bad one and a good one that was already torqued down. Depth in #4 (fully bedded in plug) was identical to #6 (the problematic, not-yet-threaded plug).
So I'm about certain the threads are blown out. Could've been the plug walking/blowing out - but the threads look good/clean enough (even before any work) that I'm wondering if this cylinder was tapped/enlarged at some point by the small town auto shop the PO used.
Eerily similar to this thread about a 2UZ in a '99 100 Series (even down to cylinder 6) except that the plug I removed doesn't have any evidence of an insert. Maybe the insert came out two plug changes ago? I dunno but at this point I may mess around and buy a Sav-a-Thread to see if it screws right in without any more cutting. Thoughts?
My next option: Time-Sert 4412e-111. It's out for delivery today so prep starts now: clean/vacuum the cylinder, turn the motor to ensure valves are closed, upgrade my janky air hose vacuum attachment to fit the big shopvac, re-watch some installs on Youtube.
Sorry to sidetrack the thread but at least we're back to the main topic of more drastic thread repair methods. Wish me luck!