So my 2001 MR2 Roadster 1.8 vvti was burning oil, both at high revs and on the overrun. I've read as much as I could on various forums to determine whether I could remove the head and sump (and hence get the pistons out) without taking the engine out of the car. I have limited equipment just the usual garage stuff, sockets, screwdrivers, lump hammer but don't have any special lifting equipment therefore dropping the engine was a non starter.
There's not much on the forums about dismantling the engine whilst in situ but plenty of "experts" on the causes of the oil burning (oval bores anyone?), seems most people are posting based on other forum's posts or word of mouth? but nobody had actually done the job with the engine still attached to its mounts.
Anyway, I did a bit of backgrounding, plenty of time spent under the car and inside the bonnet just seeing if it looked possible to do the job and I eventually decided to take the plunge and give it a go.
The main issue I could see with getting the head off is the fact that you have to remove the timing chain cover before you can remove the head and there's not much room between the RHS of the engine and the bulk head. I had a look at the manual and it seemed to indicate that you can remove the cover with the engine still in the car so...I had nothing else to do this weekend!
Well I have to report it is entirely possible and I have pictures to prove the fact.
I can report that the cause for the burning oil on my particular engine is sticking oil control rings, this can be clearly seen in the pictures where the compression rings are nice and loose and springy yet the oil rings are gummed in and not at all springy resulting in oil migrating up past the control ring and into the combustion chamber. All 4 pistons have an identical failure mechanism, with the oil control rings not in proper contact with the cylinder bore.
It does seem to confirm that the design of oil control ring is not as good as it should be. There is no real wear on the bores (may not be to Toyota's exacting standards but that doesn't mean they are beyond further use), the cross hatching is still just about visible, the pistons do rock slightly but no worse than most other engines I've stripped (quite a lot) with similar mileage (87000).
I haven't put the new rings in and run the engine so can't confirm that this will fix the problem but I am totally confident that it will and I'll give an update once the car's up and running (should be sorted next weekend at the earliest).
I haven't posted this to enter into a discussion about why the engine uses oil, this post is merely to let people know that you can do the job without removing the lump and with only the most basic of tools (although I did have to purchase an M12 splined tool to remove the head bolts).
I might add a procedure if there's enough interest.