to update anyone who was interested in my O2 sensor probs, i have replaced my old o2 sensor with a new one from toyota. it was a little pricey @ $128 vs $64 for an after market, but the only aftermarket i could find had only one wire while the toy sensor has 4 (i assume Toyota knew what they were doing when they required 4 wires to do the job...)<P>well, after a last fill up of 5.5 gallons after driving 55 miles (10 mi/gal!!!), i replaced the O2 sensor and rebuilt the idler arm while i was at it (with a prob of it's own.. see my 'idler arm bushings part #s' posting). at first fill-up since, i traveled roughly 185 miles on 11.3 gal (`16-17 mi/gal) what an improvement. the only down side is that the engine preignites a little on heavy acceleration.. (which it used to but hadn't since the mileage became poor) guess i'll have to go back to 89+ octane petrol.<P>i'm quite a suprised that an O2 sensor could cause that much of a prob with out the 'check engine' light coming on... hmmm.<P>later.gene.