[burma]

90 CRX Si with a JDM D15B VTEC/P28/DX trans

I’ve had this engine in my CRX for about 5 years, and I’ve recently noticed an increase in oil consumption. It always used a little, but now I’m adding every week as it gets pretty low on the stick. Not much smoke from the exhaust, except when the engine is over 5K RPM, then it lets out a decent blue cloud. I replaced the PCV since it’s cheap but it didn’t change anything.

I then decided to test compression, and I’m getting great numbers (~225 on all 4 cylinders). Here are the plugs (around 15k of daily driving on them):

Given that the compression numbers are good and the car is running pretty well, I’m guessing I shouldn’t worry about it for now, but the perfectionist in me doesn’t want to leave it alone. Since it mostly seems to be a problem at high RPM, I’m guessing valve seals? Is it worth worrying about right now or better to wait and see if it gets worse? Thanks

 

[Gtmorgan]

Sounds like oil rings getting weak.

[QUOTE="Gtmorgan, post: 5183009, member:
[/QUOTE]
Or the value seals

 

[drtalon123]

Did you rebuild the engine before you swapped it in? If not, shes probably due for a teardown, blueprint, and refresh.

Looks like #4 is burning the most out of all of them looking at plugs alone, which means excess oil is making it into the combustion process (intake tract, intake valve guides/seals and/or cylinder sealing), not just leaking into the exhaust (exhaust valve guides/seals).

When it smokes during high rpm, does it happen most once you lift off and let the engine naturally spin down?

If so, valve stem seals and/or worn guides are typical culprits. When you lift off at high rpm and the throttle closes, your engine does what it does best, turns into a vacuum pump that pulls a hard vacuum very quickly. If the valve seals let oil pull past them during high vacuum conditions, due to them being worn/hard/brittle, or the guides are letting the stem walk around too much, you'll burn oil most on lift off.

If it smokes most on hard accel with throttle matted wide open, cylinder seal/missing cylinder crosshatch/worn or stuck rings are suspect.

 

[burma]

Did you rebuild the engine before you swapped it in? If not, shes probably due for a teardown, blueprint, and refresh.

Nope, I actually bought the car with this setup. It’s been a good runner though.

Seems to smoke most when on throttle. So prob a sealing issue.

I guess the follow up question would be: worth it to rebuild the D15 or swap it for a B series? I am happy with the power, have good working AC, etc. so I’d be more inclined to rebuild if it isn’t too painful a process. I think I’m a pretty competent shadetree wrench but this will definitely be a new frontier.

 

[Oldcivicjoe]

A full rebuild on a d or f just dropping the long block off at the machine shop will be less than a b swap, which likely needs roughly the same treatment, so ends up being much less on the bottom line. So if you are happy with the power just rebuild the D.

 

[EGenthusiast]

I burned a litre every gas tank in my d15 worked great till I pulled the engine. Used 20w50 motorcycle oil in it because I got it for free at work for 3 years

 

[burma]

I decided to get a little more..scientific about measuring consumption and it looks like it’s not as bad as I thought.

Used about a quart over 1,000 miles of mostly city driving and that’s with a few budding oil leaks. Still don’t love the smoke but I guess I can live with it for now, even though I’m feeling a case of the “while you’re in there’s” since it’s probably due for a timing belt and water pump soon.