Question about 1999 Lexus Gs 300

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1999 Lexus GS300. Car is hesitating and can barely pick up speed no matter how hard I press the gas.

I have a 1999 Lexus GS300... Car is hesitating and can barely pick up speed no matter how hard I press the gas. Codes I am getting are P0300, P0304, P0305, P0171, P0172. When I first had it diagnosed I got a P0305 coed and one other I dont remember. They said it was either my ignition coil and/or my plugs. So I had the coil that they said was probably bad, all plugs, and the wires replaced. I used Bosch platinum plugs and NGK wires. Yet still my car is still doing the same thing and have only gotten worse. Now they tell me it must be the catalytic converter. Although I never got any codes that would suggest this (I dont think). Please help me. I am a college student that cannot afford anything as it is...

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  • Eli baron Nov 06, 2012

    I also have the VSC, VSC OFF, Check Engine lights on.

  • tracy Dec 09, 2012

    i am having same problem,lexus es300 1999



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It sounds like it could either be a throttle positioning sensor failing, or possibly a fuel injector line could be loose which will cause air into the fuel system and cuase low power and hesitation,,

Posted on Nov 06, 2012

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  • Eli baron Nov 06, 2012

    Strange that you say that because when my buddy was putting my new ignition coil in he said the throttle valve cover ( i have no idea what it is called) was only opening up a quarter of the way no matter how much he pushed on the gas. I forgot to mention that until you said something about the throttle sensor. When he showed me I just assumed it would work right when he put it back together. So where is this sensor located and is it hard to replace? How will I know for sure if that is it?

  • chad hanna Nov 06, 2012

    it should be located at the throttle pedal or it will be above it.. there is also a fuel injetcor control sensor and it will be located under the valve cover.

  • Eli baron Nov 06, 2012

    I also found a similar issue on here that someone had in which they replaced the TCS but later found out it was the Idle Valve Motor. I also have the I also have the VSC, VSC OFF, Check Engine lights on. Different codes then I have though. But your solution makes more sense than someone just guessing and telling me its the Catalytic converter.

  • Eli baron Nov 06, 2012

    Is there a way I can test these sensors before simply replacing them? just trying to avoid buying stuff a dont have to.

  • chad hanna Nov 06, 2012

    honestly, the best way is to run a complete diagnostic test , that will tell you if the sensors are operating properly

  • chad hanna Nov 06, 2012

    this will probably cost between 125.00 and 175.00... but it is better than buying parts that are not needed

  • Eli baron Nov 06, 2012

    the thing is I paid for a diagnostic test prior to this and they said it was just bad wires, Then when I replaced the wires they said "oh, it must be the catalytic converter". Should I take my car back to them and ask for a printout or something of all things checked?

  • Eli baron Nov 06, 2012

    Should I be ruling out the idea that it is a catalytic converter?

  • Michael Patton Nov 06, 2012

    ck. fuel filter



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SOURCE: 2000 Lexus RX300 6cyl 3L VVT-i "Engine Codes"!

The first and last code are your start and stop so you can ignore them the P1130 and P1150 are your two front oxygen sensors( pre cats ) bank one and two. Depending on your millage it sounds like it is time for a little maintence. Normally they should be changed at or around 60,000 kms

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SOURCE: car misfire

For the 1998 Lexus GS 300 3.0 liter DOHC

Firing Order:


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SOURCE: Issues with 92 Lexus LS 400 firing properly

fuel pump presure needs checked as does the fuel filter. injectors fail commonly and theie easy to test with a scanner just turn them on and off one at a time

Posted on Jun 10, 2010

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SOURCE: hesistaton at idle speed. how many ignition coils are used in a 98 lexus es300?

I looked it up on and it looks like there is only one coil.  You can verify that by giving them a call.  However, to me it sounds like you might be having a problem with your idle air control valve.  Since you are only having problems when the vehicle is at idle I would take a look at your IAC.  It is located on the throttle body and is usually held on by two screws.  When the IAC starts to go bad you will have problems with the vehicle when idling.  Let me know if you have any other questions.  Thanks for rating my response and for using FixYa!

Posted on May 25, 2009

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SOURCE: my engine light is blinking

It appears that there is a problem with your #4 cylinder. either no spark, or fuel. The other problem you have is with your EVAP system. Have you driven with your gas cap off or loose?

Posted on Oct 25, 2010

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