P0171 - Lexus dealer unable to diagnose
#17
Intermediate
My 1998 GS400 just had the P0171 code. My car was bogging down under acceleration up until about 3200 RPM and then it wouldn't bog as much as I got into the higher RPMs. Under hard acceleration from a stop the car would bog heavily and the CATs would pop a little bit.
After diagnosis and testing, the MAF, O2 sensors and Vacuum lines all were good. Fuel pressure was testing out at about 21 PSI versus the 44-50 PSI specified in the repair manual. Replaced fuel pump assembly (pump,filters, pressure regulator etc.) and fuel pressure is now at 50 PSI. CEL is out and (more importantly) the car runs great. MY car has 153,178 on the odometer.
After diagnosis and testing, the MAF, O2 sensors and Vacuum lines all were good. Fuel pressure was testing out at about 21 PSI versus the 44-50 PSI specified in the repair manual. Replaced fuel pump assembly (pump,filters, pressure regulator etc.) and fuel pressure is now at 50 PSI. CEL is out and (more importantly) the car runs great. MY car has 153,178 on the odometer.
#18
Pit Crew
Thread Starter
My 1998 GS400 just had the P0171 code. My car was bogging down under acceleration up until about 3200 RPM and then it wouldn't bog as much as I got into the higher RPMs. Under hard acceleration from a stop the car would bog heavily and the CATs would pop a little bit.
After diagnosis and testing, the MAF, O2 sensors and Vacuum lines all were good. Fuel pressure was testing out at about 21 PSI versus the 44-50 PSI specified in the repair manual. Replaced fuel pump assembly (pump,filters, pressure regulator etc.) and fuel pressure is now at 50 PSI. CEL is out and (more importantly) the car runs great. MY car has 153,178 on the odometer.
After diagnosis and testing, the MAF, O2 sensors and Vacuum lines all were good. Fuel pressure was testing out at about 21 PSI versus the 44-50 PSI specified in the repair manual. Replaced fuel pump assembly (pump,filters, pressure regulator etc.) and fuel pressure is now at 50 PSI. CEL is out and (more importantly) the car runs great. MY car has 153,178 on the odometer.
#19
the bank that shows lean would be the furthest from the fuel line from the tank...on a gs400 that would the be left bank if you are standing in front of the car looking in the engine compartment. On a gs300 that would be the "front" bank.
#20
Pit Crew
Thread Starter
My 1998 GS400 just had the P0171 code. My car was bogging down under acceleration up until about 3200 RPM and then it wouldn't bog as much as I got into the higher RPMs. Under hard acceleration from a stop the car would bog heavily and the CATs would pop a little bit.
After diagnosis and testing, the MAF, O2 sensors and Vacuum lines all were good. Fuel pressure was testing out at about 21 PSI versus the 44-50 PSI specified in the repair manual. Replaced fuel pump assembly (pump,filters, pressure regulator etc.) and fuel pressure is now at 50 PSI. CEL is out and (more importantly) the car runs great. MY car has 153,178 on the odometer.
After diagnosis and testing, the MAF, O2 sensors and Vacuum lines all were good. Fuel pressure was testing out at about 21 PSI versus the 44-50 PSI specified in the repair manual. Replaced fuel pump assembly (pump,filters, pressure regulator etc.) and fuel pressure is now at 50 PSI. CEL is out and (more importantly) the car runs great. MY car has 153,178 on the odometer.
Last edited by wise2k; 07-02-13 at 01:59 PM.
#21
Pit Crew
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