Car Mechs. mag, Oil burning and O2 sensor issues 1ZZ-FE

[mrzwei]

Guess we know most of this but it's a précis of a 'Help' letter in the May issue of the mag.

High oil consumption:  '... the 1ZZ-FE engines were produced between 2001/4 and the problem became apparent to Toyota 2002/3 when some cars were reaching 50,000 miles. By this time the sheer number of engines produced was vast. Toyota replaced engines and extended warranties. ...one of the main problems was insufficient oil return channels in the pistons. ...Having insufficient oil return channels in the pistons would explain the overheating of the pistons and the consequential locking up of the rings. ...the issue can be managed by shortening the oil change intervals to 6000 miles or six months.'

O2 sensor issue: '...The 1ZZ-FE also suffered from a reoccurring P0420 code set.  ...this indicated an issue associated with O2 sensors/cat/exhaust leak, but Toyota established that the ECU parameters had been set too sensitively and, as the cat aged, it was flagging the code set which would sometimes reappear after clearing...'

Interesting comment about the ECU parameters I thought. The engines discussed were mainly from the Aventis. The mag had a lot of correspondence on the article that prompted the above response and said that they may do an in depth feature.