2000 Lexus RX 300 3.0v-6 113K miles , no perceptible misfiring , but sluggish acceleration with exhaust leak and check engine light on . Codes P0171 bank one lean ,P1130 AF ratio sensor malfunction bank 1, and P1133 Bank one AF ratio sensor range performance. Customer wants T belt changed, but I advised needs root cause of CEL and poor performance checked beforehand. I drive and see that both AF ratio sensors do read close to the same voltage and appear to change but the Long term trims on bank 1 are ridiculously high. Both upstream AF sensors voltage do change , are close to the same voltage, but bank one hangs more at the same voltage for longer time than bank 2 , but the y pipe flex couple r does have a leak , and the car drives like the exhaust could be restricted. I clean the MAF see a little higher grams per second flow at idle but noticed little difference in acceleration . I pull front bank 2 upstream AF and using a small piece of cardboard lightly over the bung hole I sorta get a feel for the back pressure which did not expel forcefully enough like something does when corked up when I revved it up, so I reinstalled it the AF sensor . Then I unscrew the rear bank 1 upstream AF sensor and at idle could not tell there was any more back pressure from bank 1 bung hole than bank 2, but no assistant to rev car up I drove the car with the Bank 1 AF sensor removed from the hole , and there was no difference in acceleration, (maybe worse) so I assumed and ordered a new MAF and proceed to replace the timing belt and did the water pump because the weep hole had a lot of past seepage accumulation to risk not changing it.
Having dream of a comeback haunting me last night ,Today I cleared codes and decide to swap the 2 upstream AF sensors between banks and sure enough the ridiculous fuel trims transferred to bank 2 voltage between the AF sensors, but voltage are still close to each other above 3 volts. What makes the trim go so high on one bank with voltages between them so close ?I'm not seeing volts of one flat line at 0 or 5 volts . Drove the car to the Mexican muffler shop and got a new flex coupler welded in for $80to fix the exhaust leak and ordered a new Denso AF sensor for $114 w no tax from rockauto,(local stores wanted $180plus tax, The new Denso MAF I ordered day before for $75 w no core fee is $133 plus tax from local parts store.9In all fairness the reman MAF was about $79 with a $50 core , but I'll see how much better she runs with just the a new AF sensor.
I think next week I will hook up my Counselor 2 and try to freeze a couple screen shots of AF sensor activity of a known bad sensor to a new one to get a grasp on why. Maybe some screen freeze snap throttle shots of MAF sensor old and new, if it still popping a lean code and decide to use the new MAF sensor.
Having dream of a comeback haunting me last night ,Today I cleared codes and decide to swap the 2 upstream AF sensors between banks and sure enough the ridiculous fuel trims transferred to bank 2 voltage between the AF sensors, but voltage are still close to each other above 3 volts. What makes the trim go so high on one bank with voltages between them so close ?I'm not seeing volts of one flat line at 0 or 5 volts . Drove the car to the Mexican muffler shop and got a new flex coupler welded in for $80to fix the exhaust leak and ordered a new Denso AF sensor for $114 w no tax from rockauto,(local stores wanted $180plus tax, The new Denso MAF I ordered day before for $75 w no core fee is $133 plus tax from local parts store.9In all fairness the reman MAF was about $79 with a $50 core , but I'll see how much better she runs with just the a new AF sensor.
I think next week I will hook up my Counselor 2 and try to freeze a couple screen shots of AF sensor activity of a known bad sensor to a new one to get a grasp on why. Maybe some screen freeze snap throttle shots of MAF sensor old and new, if it still popping a lean code and decide to use the new MAF sensor.
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