there is some material on this if you search but nothing especially definitive.

i pose this question to those with engine building or simply long 240 experience.

i have never seen or had an engine with a bad rod before and i have owned and worked hundreds of these cars. this includes very high mileage cars, engines with broken oil pumps and still driven lightly and cars badly overheated requiring a new head because the old warped so badly. yet in none of these cars was there ever a rod knock like i heard today in a genuine 120xxx mile 92 240 wagon in impeccable condition owned by the same woman since 1993.

oil pressure cold is 60 psi and drops only slightly once warm.
at cold startup the knock is so loud you can hear it 20 feet from the rear of the car. if seems to vibrate through the exhaust pipes. once the engine fully warms up the sound almost disappears.

i have had engines with piston slap but nothing ever like this. logic suggests to me that rod knock is always present and worse as your increase the rpms. can piston slap really mimic a bad rod knock in severity?

can a bad knock sensor cause what i am hearing at idle?

i welcome any suggestions to pin this down with more than guesswork and voodoo.

i hate to pull engine unnecessarily.