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Weird oil consumption + oil cap coming loose?

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Weird oil consumption + oil cap coming loose?

Postby ossy » Fri Jan 12, 2018 10:30 pm

Hi, I'm having some weird oil consumption problems on my 1ZZ 2001 MR2 Roadster. I know the preface engines are known for having oil consumption problems but this is strange, really hoping someone can help.

It's on 90k miles. It's perfectly fine and uses no oil at all when driving normally but soon as I put foot down and hit limiter a few times or something when VVTI does the slight cross over around 6k RPM, it will lose around 200-300ml (around quarter of dipstick) in matter of minutes and the engine oil cap comes loose but oil is not leaking out. I've been checking oil levels regulary and been testing this over a period of 3 weeks.

There's no oil leaks underneath car and no blue smoke from exhaust, however the flexipipe is slightly bust. Had a friend follow me the other day when I put footdown to test and he said he couldnt see any blue smoke either.

- The precats were removed ages ago and were perfect condition
- I've tried switching to thicker 10w40 oil but no difference
- Tried a can of Wynns Stop Leak
- Changed PCV on Wednesday night

Non of the above have made any noticable difference. Any ideas what the problem may be?

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Re: Weird oil consumption + oil cap coming loose?

Postby 1979scotte » Fri Jan 12, 2018 11:49 pm

That's a strange issue not heard of anything like that before.
Btw vvti kicks way down the rev range closer to 4k rpm than 6.
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Re: Weird oil consumption + oil cap coming loose?

Postby jonbill » Sat Jan 13, 2018 8:34 am

Try a new PCV?
If it’s blocked maybe there’s pressure in the cam cover, forcing oil past the valve stem seals and loosening the cap.
Could be wrong, I’m never sure which way round the flow is with PCVs.

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Re: Weird oil consumption + oil cap coming loose?

Postby shnazzle » Sat Jan 13, 2018 8:42 am

If you're not burning it, you're leaking it.

Any signs of heavy leakage?

Modern oil doesn't necessarily burn (blue) visibly.
Compression test may be handy.

My thought was pcv but you've replaced it
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Re: Weird oil consumption + oil cap coming loose?

Postby Carolyn » Sat Jan 13, 2018 8:59 am

For the oil cap to unscrew itself, it must be getting hit with pressure pulses. I suspect your piston rings aren't dealing with the pressures at high revs under load. If that is the case, a compression test would show higher than expected pressure, probably. It should be somewhat below the factory spec 185 psi. If it's higher than that, oil is getting past.
All the oil gets consumed as fuel in such a case, so you won't get blue smoke. PCV would show blue smoke...
(You could just not rev it so high....)
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