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Sonya 10/2/2012
2002 Jeep Grand Cherokee Limited 8Cyl4.7L - Transmissions & Drivetrains
would my fuel pump cause me to have code 300 and multi misfires,
I have multi misfire codes and when i try to speed up to pass another vehicle, i get hesitation until i drop below 3000 rpms? Now it barely has any power.
2 Answers
  • HouseCallAuto
    HouseCallAuto 10/2/2012
    yes it could, but to confirm that, all you need to do is perform a fuel pressure test using a fuel ptressure gauge and hose adaptor. Attach the pressure gauge to the schrader valve on the fuel rail and start the engine and read the pressure. It should be 49 PSI plus or minus 5 psi. Then, the dieal thing is drive the vehicle with the gauge still hooked up by looping the hose through the rear of the hood by the wipers and when you are feeling the loss of power, view the fuel pressure reading and if it is withinnthe range I said, then your fuel pump is not your cause.
    Sonya 10/4/2012
    Thankyou, i did this and it reads 51 psi. Im getting codes 300,303,304,420,306,307 and 432. I was told maybe a problem with my transmission, because the hesitation when i step on the gas, but it has loss alot of power and kinda puts a little bit.
  • HouseCallAuto
    HouseCallAuto 10/4/2012
    You have a clogged catalytic converter assembly and the exhaust gases cannot escape. This will always cause multiple misfires and direct misfires and in some cases a catalytic converter efficiency code of which you have two of - the P0420 and the P0432. It is very safe to say that you should replace the catalytic converter ass'y (y-pipe) and at the same time, replace all the oxygen sensors. You problem will be gone. probability here is 100%.

    Added note: in some cases the catalytic converter substrate breaks up and actually exits the converter shell and can become wedged in rear catalytic converter which does not go bad often. that being said, check for any loose broken pieces in the inlet of that converter after the y-pipe is removed and remove them of course with a shop vac with a small hose attachment.
    Sonya 12/17/2012
    Thanks again, I have now replaced all 8 plugs, 4 coil packs, the y pipe, the air filter and the 2 front o2 sensors. I still have no power? What else can i do?

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