Back in this thread again, 50k miles later, with 224k miles on the odometer.
Misfiring came back on and off over the last year. Replaced the plugs at 202k and 208k which temporarily fixed the issue each time. No coolant consumption up to 208k miles.
Beginning at 221k miles, it happened almost every cold start. Misfires go away in less than 1 min.
Beginning 223k miles, it happens closer to > 50% of all combustion starts (cold or hot). Coolant consumption is now half the expansion tank every week. MIL on, misfire codes on cylinders 1-4.
Brought vehicle for head gasket replacement quotes at 3 non-Lexus repair shoppes.
Quote 1: $3500 for head gasket replacement + $1000 for timing chain replacement (optional, recommended). Parts, materials, labour included. 1 week turnaround.
Quote 2: $2900 for head gasket replacement. Parts, materials, labour, alignment included. Oil and oil filter explicitly included as well which may not be compulsory in the job but it was offered. 1 week turnaround
Quote 3: pending
If I DIY, it’s probably $750 estimated in parts for head gasket + timing chain. Anticipates no other issues, like bent rod or machine work to minimal deck (-0.002”) the mating surfaces. Time needed is 1 week of my time stretched over several nights after work and weekend. Already have 2nd vehicle so no rental cost accrued. I’m not super young anymore but could probably handle it.
Really hate outsourcing that much for a repair on a vehicle only worth $5k.