Negative Long Term Fuel Trims?!

[hypojames]

Hi, I have a 2006 1MZFE Rx300 with long term negative fuel trims between -8% to -10% on both banks.

 

So I understand the car is reducing injection time to lean out the mixture but I don't know if there are any common issues with 1mzfe engines that cause this rich running.

Are the fuel Pumps/Pressure regulators common to fail and cause high fuel pressure?

Are Mass Aiflow Meters a likely culprit? (I would think likely this)

Or maybe just worn O2 Sensors?


Car has 115k Miles on the clock. Full service history runs all nice and good.


Thank you for any input.

 

[Tumezi]

Hi, 

Have you checked are the injectors leaking, the pressure on rail should stay quite long on nominal values if they doesn't leak.

Maybe try some 10 euros costing injector cleaner additive and check does it helps? 

[hypojames]

3 minutes ago, Tumezi said:

Hi, 

Have you checked are the injectors leaking, the pressure on rail should stay quite long on nominal values if they doesn't leak.

Maybe try some 10 euros costing injector cleaner additive and check does it helps? 

I doubt leaking injectors because both Banks/either side of the V6 are reporting the same negative fuel trims. 

 

I do need to verify the fuel pressure for sure. Do the 3.0 engines have easy fuel pressure test point?