Hi. My 2006 Rx300 with the 3.0 vvti engine has around -10% long term fuel trims on both Banks.

I've changed the Maf new genuine toyota. I also changed the fuel pump assembly just incase fuel pressure was too high. No difference.

The car has 116k miles. Do there air fuel sensors start to misread the mixture coming down the exhaust when they get old?

Thank you for any help

 

Yes they do. Can't remember if trims go positive or negative (not a diagnostic expert at all) when the sensors age. What is your mileage like?

 

I am not sure on how-to guide you, looking forward to see the suggestions of others.

 

i am betting on a vacuum leak

 

Negative fuel trims are sign off too much fuel. Not a vacuum leak.

I changed the air fuel o2 sensors now. Still negative trims.

I can only really put it down to injectors flowing/leaking abit more than they are supposed to. Car runs so well though.