Burning LOTS of oil, help?
I have a '91 Honda Civic HB, D15B6 engine, and it is burning a quart of oil every 120 miles or so...about 3 quarts per tank of gas. This is a stock engine, no performance parts on it (yet). It does not smoke all of the time...when I'm off the gas it doesn't look like it's smoking, it doesn't smoke when I first start it up, and sometimes the smoke is not noticeable at different throttle levels. However, sometimes when I am on the throttle, the smoke billows out behind me, whether I am on it lightly or close to WOT, but not every time. Also, it seems to smoke more coming out of a corner, but again, not every time.
Here's when it started and work I have done to the engine so far. When I got the car it ran on 3 cylinders and smoked a little when it was cold. Not much, it didn't use much oil at all. I checked compression and found that the #3 cylinder had less than 25psi, the others were about 125psi. I took it on a 3 hour trip on the highway, and by the time I got back it was running worse...now it had less than 25psi on cylinders 1 & 3. I found it was leaking compression out the exhaust, so first I tried cleaning out the cylinders, just in case it was a piece of carbon stuck in there not letting the exhaust valve close. To do this I ran the engine around 2,000 rpm and poured about a quart of water in the intake through the throttle body....it was pretty gunked up, the resulting steam out the exhaust was black initially instead of white. After that, I poured some ATF in the same way to re-lubricate the cylinders. After running it for a bit to burn the excess oil out of the cylinders (and get rid of the smoke), I checked the compression again and found no change.
So, I pulled the head and found I had 2 burned exhaust valves. I replaced the two burned valves, cleaned up all of the others, lapped them, replaced the valve oil seals, and put it all back together. I did not take the oil control jet out of the block and clean it when I did this. I put it back together with new intake and exhaust manifold gaskets and a new head gasket, and started it up. It ran great, but it smoked quite a bit. I drove it for a few miles, and it did not seem to smoke any less, so I took it back apart again. This time I took the head to a machine shop, they pressure tested it and found no cracks and milled it. This time I pulled the oil control jet out of the block and cleaned it up before I put it back together. I also bought another set of valve seals and replaced them again, and lapped the valves again. I put it all back together (new head gasket, but I re-used the intake and exhaust gaskets), and ran it again. Once again, it runs good, but it smokes. I have found from driving it that if I drive it carefully, it doesn't seem to smoke as much, but it still burns a quart of oil in about 120 miles.
The last thing I did was disconnect the pcv pipe from the air intake hose. This did not make it stop smoking, but it also is not blowing any oil residue out of that pipe....I have had it disconnected for about 60 miles of driving, and there is no oil in the engine compartment and no oil leaks (other than what is burning).
Any ideas from anyone of what can be causing this engine to burn that much oil? There is no oil in the antifreeze, no antifreeze in the oil. I don't think the rings are leaking, because there doesn't seem to be pressure in the crankcase (no blow-by out the PCV). I don't think it's the valve seals for two reasons: 1 - I replaced the seals twice; 2 - It doesn't smoke on the initial start-up. Does anyone know what the oil control jet does? If that is clogged or bad, could that make it burn oil and smoke?