87 Oil/smoke during start question

[F16driver]

I recently read a post that suggest that just prior to shutdown, you can rev the engine up to approx 2000 rpm for 30 seconds and then shutdown and the end result is less oil smoke during the next startup. I tried this a few times and have had a significant improvement(less smoking) during start. Can someone explain why this works and if my car doent smoke at any other time , whats the most likely cause of my 87 carerra smoking during startup. I keep the oil level at the suggested mid point on the dip stick. I have 130,000 on the motor , no rebuild yet, still running strong, but I use about 1-2 quarts per 1000 miles, dependind on how agressive I am with my foot.
Thanks,
John P
Original Owner

[T77911S]

here is what i have come up with from observations of my car (it too smokes when first started ). when it sits, all the oil drains back into the engine and perhaps high enough to get into the cylinders and leak past the rings. when i fill the oil to the top mark, it seems to got through oil much faster and smoke more at start-up. i have done a compression check and all 6 were very close to 165 psi. so i would not go and replace rings because of this. if it does not smoke under any driving conditions( accel or decell) , i would not worry. some may say guides or valve seals but those would show their tail when you drive it, especially hard. by the way, i bought my car with 80k miles and it would at blow a cloud of smoke at start-up only.

[F16driver]

TT77911,
Thanks for the reply, After reviewing many of the previous post on this subject I too agree that right now my smoking is not a big problem. I am still wondering, if anyboby can explain, why letting the P car idle for 30 seconds before shutdown reduces the amount of smoke at startup??

[livi]

At idle more oil is pumped back to the oil tank, thus minimizing the amount left in the engine that eventually will cause smoking at upstart ???

Just an uneducated assumption..

[wolf]

Most smoke on starting is condensation in the exhaust system. Some is oil seeped into the cylinder. No problemo.

[Early_S_Man]

The oil smoke puff on startup isn't from the cylinder, is NOT from leakage past rings, and isn't being burnt in the cylinder!!! I have seen many cases of oil smoke puff on startup that showed no trace of oil on the sparkplugs.

The quantity and duration of smoke is directly related to collected volume of oil in the sump, and duration of exposure of the exhaust valve guides to the 'under oil' situation. The oil seeps up the exhaust valve guides past the white Teflon valve stem seals and drips into the heat exchanger ports, and ultimately into the muffler if the situation lasts long enough -- weeks to months. Because the seepage past the Teflon valve stem seals is very, very slow, the oil puff is reduced in volume or eliminated completely if the engine was run at idle long enough for the scavenge pump to evacuate the sump before shutdown ... especially if the next startup occurs in a week or less.

[cbeers]

you can rev the engine up to approx 2000 rpm for 30 seconds and then shutdown and the end result is less oil smoke during the next startup.

I see you changed that to IDLE for 30 seconds

Warren has it nailed.

-Chris

[T77911S]

i drove my car to work today and at lunch, poof, a nice big blue cloud of smoke.
are my valve seals so bad on a motor with 85k miles it would leak past in 5 hours? it wouild only take a little oil past the rings to smoke at start-up and it would burn off so fast it would not show on the plugs, plus it would not reach the plugs since it is such a small amount.
would it be easier to leak past when the piston is at BDC?
i dont see smoke any other time while driving.