Weird oil consumption + oil cap coming loose?

Ozzy · January 12, 2018, 22:30

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?

1979scotte · January 12, 2018, 23:49

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.

jonbill · January 13, 2018, 08:34

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.

shnazzle · January 13, 2018, 08:42

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

Carolyn · January 13, 2018, 08:59

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....)

Ozzy · February 1, 2018, 14:31

An update incase anyone wants to know or runs into a similar problem in the future.
I had both dry and wet compression tests done to check if engine is healthy before spending any more money, and not good.

Dry
----------------------------
Cylinder 1 - 150 PSI
Cylinder 2 - 150 PSI
Cylinder 3 - 50 PSI
Cylinder 4 - 110 PSI

Wet
----------------------------
Cylinder 1 - 170 PSI
Cylinder 2 - 170 PSI
Cylinder 3 - 150 PSI
Cylinder 4 - 160 PSI

Seems like the valve seals are gone as pouring a small amount of oil into the cylinders one by one created a seal and got the pressures back up. Cylinders 3 and 4 still did require a couple of more cranks unlike the first two but sparkplugs were the culprits of that. Giving the tips a light sand solved that and the TRD oil cap just got worn down with the constant topping up I think. New cap stays nice and tight.

It's driving fine so going to try and keep it going for now as it only burns oil at high revs. Gonna keep a lookout for a cheap replacement engine or might start looking into the 2zz or k20 swaps if affordable and see what's required, I don't know :/

Carolyn · February 1, 2018, 17:29

I'm afraid much of what you just said makes no sense at all. Why would bad valve seals not result in wet rings, and artificially high compression)? Spark plugs have nothing whatsoever to do with compression (unless they're cross-threaded in the head).

Your piston rings are shot, I'm afraid. Time for a rebuild. Not the end of the world, though.

Ozzy · February 6, 2018, 10:34

I thought the same but I'm sure that's what I was told, unless I misheard. Was quite disappointed seeing the low compression and sorta zoned out tbh lol.

Either way... Engine rebuild is an engine rebuild unfortunatly. Knew I was gonna regret buying a 1zz MR2 as a cheap run about. Atleast he gave a good price for fitting replacement engine.

Also, the sparkplugs were sanded because the mechanic said it sounded abit rough like if it was misfiring and said car was running rich. I assumed it was just the exhaust but guess it was as it sounded much better after.

Carolyn · February 6, 2018, 10:54

If the person who told you the stuff about valve seals and spark plugs is the one who quoted for fitting a rebuilt engine.

Find someone else.

where are you based?

Ozzy · February 6, 2018, 11:26

Cornwall and I'm confused. Why would dirty sparkplugs not help with misfiring and slow startup? He used battery pack as well incase it was the battery or starter which makes sense.

A lot of people suggested him on Facebook and he's well known for doing engine and turbo conversions for Jap cars. He only suggested a replacement engine as a cheaper, less time consuming fix. He must have said oil rings and I'm just a pleb getting confused from everything he said lol. He also had a Glanza in the back with a turbo 2zz conversion that he's done for someone so must know his stuff.

Carolyn · February 6, 2018, 12:24

Fair enough. I think I got the wrong impression!

paulj · February 6, 2018, 21:31

Ossy, sorry to hear your news. No problem being confused I think I would have zoned out after hearing oil rings on my car!

Suggest going back to have another chat with your man once you have taken in the situation and have a clearer head - perhaps take a mate with you so that two of you are listening and getting the full answer.