On model year 2000-2002 Spyders, there was a known problem with piston rings 'sticking' on the 1ZZ-FE engine; Toyota issued a Technical Service Bulletin to its dealers in the UK (but not the US). Toyota changed the design of the piston rings on the 'facelift' version of the Spyder introduced in late 2002 as a 2003 model.
It is the source of much "chicken or egg" debate whether itís a case of:
(1) Stuck piston rings fail, which causes oil to drip onto the pre-cats, which leads to pre-cat deterioration from oil exposure, which results in pieces of pre-cat sucked back into the engine, scratching and scoring the cylinder walls, which leads to more oil passing by the piston rings and being burnt off without you even realizing it, or
(2) The pre-cats break down due to age and blow into the main cat causing excessive back pressure, which leads to leads to greater oil blow-by, which leads to more oil passing by the piston rings and being burnt off without you even realizing it.
Regardless.. it's a very bad thing either way. Common symptoms of pre-cat failure are (1) extreme oil loss and (2) lack of power all the way through the rev range. By the time the oil pressure warning light comes up, it's too late to do anything.. thereís almost zero oil left in the engine.
There are isolated cases reported on the forums of 2003+ models (which had improved piston rings) suffering pre-cat failure.. so the piston ring design did not eliminate the problem. Ultimately, there is no hard evidence available to conclude on which is the cause and and which is the effect.. and Toyota isn't interested helping prove they sold a car with a defective design given the low sales volume of the vehicle and cost to repair.
All we know for certain is that, while you canít remove piston rings from the engine, you can remove the pre-cats from the exhaust header manifold. If you have no pre-cats, there's nothing to get sucked back into the engine.
Last edited by RPAltman; 09-12-2012 at 05:26 PM.