Intermittent smoking

[habusake]

I have a 97 240SX with 89k miles that intermittently blow a puff of seemingly blue smoke. It doesn’t smoke at start up nor when you floor it. It only seems to smoke when accelerating from a standstill. The car has not been driven hard; I have owned it for 11 years. All 4 plugs look clean. I have been getting O2 sensor error codes. The code cleared after replacing the front sensor, but came back in two weeks. I’m pretty sure it’s running very rich. Also,I know this is strange but it hardly smokes with the AC on. The symptoms don’t seem to apply to either rings or valves. I’d appreciate any advice before I take it to Nissan.

[asoomal]

Sounds like valve stem seals.

Perform a compression and a leak down test and post your results.

[habusake]

OK,I'll do that. But woudn't valve stem seals leaking cause smoking on a cold engine start up?

Thanks

[compactfean]

Only on severe cases. The reason it would smoke after sitting for a min, would be because the vacuum from throttle body being closed would suck oil past the intake valve seals.