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I Have A 2001 Is300 And My Cel Is On. Codes Read Are P0171 And P0174.... Im Getting Horrible Gas Mileage And Also When Ever I Try To Stomp On The Gas Or Try A Jackrabbit Take-off My Car Hesitates And And Doesnt Take Off. Instead It Feels Like Its Chocking And Drops In Rpm's. If I Keep My Foot Down On The Gas It'll Continue Like This And Not Pick Up Any Speed. Also, If Im Idling And I Floor It Or Half-way Floor It. The Engine Will Double Rev. From 1000 Rpm It'll Go To 2500 Rpm, Drop To 1000 Rpm Then Go Up Again. Please Help Me Out Here. Also If This Helps... I Just, Like 1 Week Ago, Changed My Spark Plugs. I Have An Aem Short Ram Intake But This Whole Thing Happened Even When I Had The Stock Intake. Thanks In Advance.
 

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P0171 & P0174 puts out the same DTC, system too lean ( fuel trim bank 1 & bank 2). It could be your MAF sensor or the O2 sensors, but there are other areas to check that could be wrong.
Air induction system.
Injector blockage.
Engine coolant temp sensor.
Fuel pressure.
Gas leakage on exhaust system.
MAF sensor.
Open or short in O2 sensor (bank 1, 2 sensor 1)
ECM
Fuel trims refers to the feedback compensation to the basic injection time. There is the long term fuel trim and the short term fuel trim.
Short term fuel trim is the short term fuel compensation used to maitain the air-fuel ratio signal from the o2 sensor which indicates the air-fuel ratio is rich or lean compared to the normal value, causing a reduction in fuel volume, if it is rich, and an increase in fuel volume if it is lean.
Long term fuel trim is the total/overall fuel compensation carried out long term to compenesate for continued deviation of the short term fuel trim from the normal value. 3 factors affect this: wear over time, changes in useage and individual engine differences.
Your CEL will come on if both the short and long term fuel trims are rich or lean beyond the normal value.
 

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sounds like the car is going into safe mode... your MAF sensor is throwing a bad code. you have to take it to the dealer and have them clear that.
 
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