Good compression, but still burning oil. Help!

[leukram]

I have a 96 metro 1.0L (3-cyl). It has 47,000 miles. It seems to be burning about 1qt of oil every 300 miles. It is not leaking anywhere. I don't get a smog cloud behind me when I drive down the road, but if you put your hand in the exhaust, specks of oil accumulate. I have performed a compression test on the engine at operating temperature, and I get about 175-180 psi on all cylinders when pressing and holding the accelerator while turning over the engine (about 130 psi if the accelerator is not depressed; I'm not sure which way is proper). I am at a loss as to what could be the cause of my oil burning. I have noticed that the PCV valve seems to foul about every 1,500 to 2,000 miles. It fouls with a yellowish brown vasoline like substance (gas/oil??). When it fouls, oil gets into the breather/ throttle body. I can understand the oil burning in this situation, but I get oil burning regardless of the PCV valve condition, because oil burning still occurs even with a new PCV valve. Other than everything described above, the car runs well. It idles fine. It gets about 37-40 mpg (which seems a little low). Any suggestions or ideas as to what could be causing this problem would be appreciated.

Oh, I almost forgot. The check engine light is on. I have followed the procedure to get the code, but no code is given. The check engine light stays off for about 30 miles, but then it comes back on. The person I bought this from (at 43,000 miles) said that it came on soon after the dealer replaced the EGR valve (at 37,000 miles). When she asked them about it, she said that they said that some carbon probably fouled a sensor. However, they didn't offer to look at it or fix it.

[geozukigti]

well, if you're getting specks of oil, that's not burnt, and your spark plugs aren't fouled... Sounds like you have a valve seal leak. You can have the head rebuilt for about $100-$125. It should only take the shop a day or so. If you want some more compression, have them shave .015" off the bottom. That should bring you up to about 190psi(5psi over new stock). Or if you want it to run nicer on the freeway and in the low end, have .020"-.030" off. .030" will bring it up to about 210psi. But you'll have to use mid-grade fuel. But she'll run niice, and get better MPG in-town. I had .030" shaved off my 1.3DOHC head(215psi stock compression) and now i'm getting 245psi on all 4 cylinders. I NEED to run 94, or better as a result tho. But the engine comes alive with more compression. For a nice daily driver, I'd go with the head rebuild/valve job, and .015" off the bottom. She'll run like a champ.

[leukram]

Thanks geozukigti! I ran across something on the internet today about an oil control ring that seemed to be a likely candidate for the cause of my problem. Specifically, it talked about blowing unburned droplets of oil out of the exhaust. Which do you think is more likely the problem, the valve seals or the oil control ring? And, do you think it is worth it to repair either of these possible problems?

[geozukigti]

If you're only losing 1qt/tank, that amount of oil loss would be burnt in the combustion chamber. Not guaranteed, but most likely. Check and see if your spark plugs have any oil on them. If they're dry, I would almost rule the ring out, as being the problem. Perhaps run the engine for a few moments with a spark plug out, and stuff a white rag in the spark plug hole. See if any oil gets on it. Hold the rag in the hole tho, the compression will blow it away, or possibly suck it in! heh. If it's clean, with just gasoline on it, your oil loss is happening after the combustion chamber. AKA, the valve seals or valve guides. Do the rag test on all 3 cylinders. It only takes 1 bad ring to pass oil.

[leukram]

Thanks for the helpful information. I haven't had a chance to do the rag test, but I will as soon as I can. I can tell you that the plugs are perfect. There is no sign of oil fouling or burning. They have a light gray, tan color.

I did check the exhaust and found that I may have over assumed on the oil specks. I found that it only seems to do this after it has sat for several hours. Once the engine heats up, it no longer spews out the oil specks. Also, it does not seem to spew oil if I let it sit for an hour and cool off. I notice the oil in the exhaust in the morning and when I leave work. But, at least tonight, when I got home, there was nothing but hot exhaust coming out of the tailpipe. The weird thing, is that I never get a blue puff of smoke, or any smoke for that matter, when I start it. The only noticeable exhaust is in the morning. It is white like condensation, and it goes away after a few miles down the road. At least I always assumed it was condensation because it's white, it only appears on cold days, and it goes away after the car warms up.

Any ideas on all this? Oh yeah, and any ideas on why the PCV valve gets fouled as soon as it does? Could there be any correlation to the valve seal/ guide theory? Thanks for bearing with me.

[avfan]

I would lean more toward the valve seals than the oil ring most notably because the symptoms seem to go away when engine is warmed up -this is typical valve seal behavior when they start to go bad

[leukram]

Well, I did the rag test. I didn't notice any oil on the rag, but the rag did turn a tan color. It also got very dried out and brittle, which surprised me. I only held it on each cylinder for ~10 seconds. I used a flashlight to look down into the cylinders through the spark plug hole. All three cylinders had tan, light red deposits near the middle of the piston head, and very dark black (carbon) deposits near where the exhaust valve would be located. On one cylinder, it looked more sludgy than dry burnt on carbon soot. Also, the PCV valve and breather already has the build up mentioned before, so it seems to do this quicker than 1500-2000 miles - more like just as soon as you clean it, it starts to build up. Any ideas or comments would be appreciated. Thanks!