Elle <honda.lioness@gmail.com> wrote in news:c09cc0ba-7584-4ec3-8546-
1473c91deb26@g1g2000vbr.googlegroups.com:

> 1993 Civic DX, 197k miles. Purchased in July 2008, with me as second
> owner. In March 2009 it started burning/losing oil at about a half-
> quart per 600 miles.



That's a quart every 1,200 miles. Not good at all for less than 200K
miles.


>
> -- Several times over the last couple of months I have thoroughly
> inspected the areas of the usual seals: dizzy o-ring, front crank and
> cam seals, valve cover gasket, upper and lower spark plug tube
> gaskets, oil pan gasket, rear engine seal. No leaks in these places
> that I can see.
>
> -- Replaced PCV valve a month ago. No change.



The idea that a plugged PCV valve by itself will increase oil
consumption is common but erroneous.



>
> -- Coolant level is steady; no signs of a head gasket breach.



A good sign.



>
> -- Runs superbly, otherwise. 42 mpg averaged over 24 tanks of gas
> since March. I wonder whether the oil burning has upped the MPG a bit.



I suppose it's possible. The oxygen sensor would detect the excess
hydrocarbons from the oil and compensate by reducing injector pulse
width.

Modern motor oil is a readily and cleanly combustible hydrocarbon mix.



>
> -- Inspected the spark plugs. They do not have black oil residue on
> them but all four are an odd, textured color of brown and not the
> usual properly combusting spark plug color.



Can you supply a clear photo of the plugs?



>
> -- Replaced valve stem seals a week ago. Still consuming oil. Thought
> it might be the valve stem seals especially because driving down a
> mountain using much engine braking yielded a report from buddies that
> smoke was blowing out of my exhaust. One buddy said it seemed blu-ish.
> Others were not sure.



Smoke on overrun indicates worn rings, not valve guide oil seals.

I think you need to have a compression test done. If the readings go up
for the wet test, the rings are very worn.



>
> -- Yesterday discovered the o-ring on the breather chamber had
> permatex ultra-gray or similar on it, apparently as a temporary fix.
> Also found oil residue beneath the hose connection to the breather
> chamber. I cleaned the chamber up and replaced the o-ring. I
> Hondabonded (I know, cheap) the grommet where the PCV valve hose
> connects to the breather chamber.
>
> Questions:
> 1. When an oil ring or the valve guides fails, is it usual for all of
> them to fail at about the same time, thus explaining why the spark
> plugs are all the same color? This does not pass my common sense test,
> but maybe experience is a better substitute for common sense..


They won't necessarily fail all at once, but it only takes one cylinder
to fail for smoke to show out the tailpipe. Two things you can have in
that case: A slightly lumpy idle, and an odd-man-out compression test
reading on one cylinder.


>
> 2. My theory with the breather chamber is that it was running at
> atmospheric pressure or so, and this may be higher than the usual
> pressure, meaning the PCV valve was open more often and wider yada
> than it should be. Comments?



I have a feeling you'll find that one cylinder has much lower
compression than the others.

If one cylinder is much lower than the others, there's a tiny
possibility that the rings are simply carboned up and not sealing as
they should. In that case, long-term use of Mobil 1 and some occasional
spirited driving may free it up.

By the way, when was the last time you checked the valve clearances?



--
Tegger

The Unofficial Honda/Acura FAQ
www.tegger.com/hondafaq/