I have an B16B (next to the D14A3) for 4 years now. And each year I needed some squinting with the eyes to pass MOT. Never really wanted to talk about it (something with re-sell value of the engine), but since I can't get myself to sell the engine and car anyway in this condition, why not share my problems.
Here it is, I have always had too much CO (0.3 to 1.5% on diverging rpms, circumstances) together with unburned fuel and unburned O2. So flame dead. Tried many many things, very elaborate ECU tuning, cilinder switch off to see if there is one cilinder causing this or all (the answer is all equally bad). Tested for compression, changed valve seals, changed head gasket and things only detoriated over the years.
Now I removed the pistons... cilinder walls are like mirrors and piston rings are gone. Completely worn out. Talked to some expert today and they pointed out to me how a new ring should look like and a ring that is up for replacement. Mine was way worse than that. So I'll get a new cilinder hone, piston rings in the engine and hopefully that is the end of it.
It has to be because all else has been tried and/or excluded. But the most disturbing is the fact it does not use that much oil. Easily 4000 km before it needs 1 liter. Depends on driving style, on the track I loose an entire liter within 2 hours... but that is track. That was why I was looking to the wrong direction for years.
I know that exhaust valves are black from oil since last year (I did head gasket change) and I have carbon deposits on top of the piston. Which points to oil. Since I replaced valve seals and yesterday I saw that both upper and lower blocks are silver from the inside (extremely clean, especially compared with my exhaust fumes) there is only this mechanism I believe in:
- piston rings are gone
- oil is forced upwards
- but oil is not forced downwards
- oil burns in combustion chamber during low throttle (95% of the time or more)
- oil deposits cool down or change burning, extinguishing flame at the valve and combustion chamber boundaries
- leading to very nice bhp (203 on 1.6 liter)
- but leading to unburned mixture both O2 and HC... which I guess is normally burned closer to the walls and after exhaust valve in good engines
I never gave up on this engine because I really want to learn from it... throwing an engine away and buying a new one is not learning. Hopefully I can inspire others to continue bug fixing their engines or maybe help identifying this problem for others.
![Wink ;)](./images/smilies/icon_e_wink.gif)