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Random Misfire and Bank 2 02 sensor

Discussion in 'GM Powertrain' started by UBSTANG, Dec 31, 2009.


    UBSTANG New Member

    `1997 suburban 1500 4x4

    Okay I just got this burban an the check engine light was on so I hooked it up to a OBD2 scanner and it told me that it has a p0300 which is a Random Misfire, and also Bank #2 02 sensor was at fault.
    I have noticed that it does not have all the power it should and also it misfires at a idle , and sputters at times while driving, but then sometimes you will be driving and it will kick in and feels like you have a powerband on it. Majority of the time it is just sluggish feeling.. This Morning it wouldnt start right up like normally, took a few tries, so I thought about fuel pressure.. I checked the fuel pressure with it not running and it went to 60psi without running, soon as I turned the key back off it dropped to 20psi, shouldnt this hold the pressure ?? isnt it a closed loop and maintain pressure ????

    This is my first Chevy and I dont know much about them, specially being TBI. So anyone know what would cause this ? I dont have alot of money to play trial and error with as I have been laid off for awhile ..
    Hope someone can pin point something or explain how to do trial and error test..

    Okay I just did some more random testing, key switch on truck not running fuel pressure spiked to 60psi and rapidly dropped to 20 while key is off.
    Truck started fuel pressure went to 52psi and when i gave it some gas it spiked to 60psi

    Attached Files:

    Last edited: Dec 31, 2009
  2. azdrtdog

    azdrtdog Epic Member 5+ Years 100 Posts

    Yup it should hold for at least a ten count sounds like check vavle in pump or fuel press. diaphram pull vac. line and check for fuel
    Last edited: Dec 31, 2009
  3. dwill3015

    dwill3015 Epic Member 5+ Years ROTM Winner 1000 Posts

    You have a bad coil pack on one or more cylinders. This has happened twice on my wife's 01 suburban. Hers had the same codes and ran horrible at idol and was under powered. The first time we could not figure it out and replaced the fuel filter, sparkplugs, wires only to have to take it to the dealership and they found a bad coil pack on #3 cylinder. The second time was just a month ago and gave the same symptoms so my local repair shop found the coilpack on #8 was flatlined when it was tested. It was an easy fix. Have someone check the voltage on your coilpacks.
    Last edited: Dec 31, 2009

    UBSTANG New Member

    so your pretty sure its the coil packs ? I was wondering about them myself, I did alot of research and seems like this is a common problem with these. Also not to mention no one has posted the solution to the problem.. So what would make my fuel pressure not stay at 60psi while the key is off ?

    Where is the vac line located at on the chevys ? im not familiar with this truck at all ? I think someone or somewhere it said under the upper intake ??
    an what if there is fuel in the vac hose ?
  5. dwill3015

    dwill3015 Epic Member 5+ Years ROTM Winner 1000 Posts

    I'm not too savvy on the fuel system issues but if you are maintaining some good pressure while running then it does not sound like fuel is your issue for the misfire.

    UBSTANG New Member

    thats what i was leaning towards but then again it has me second guessin myself because isnt it supposed to maintain the 60 psi once the key is turned on and back off,

    i turn the key to ON and it spikes 60psi as soon as i turn it to OFF it drops to 20psi.. i thought it is supposed to maintain the pressure
  7. azdrtdog

    azdrtdog Epic Member 5+ Years 100 Posts

    Its a 97 it dont have coil packs

    UBSTANG New Member

    im not a chevy man, but im learning,, whats it got them ?
  9. azdrtdog

    azdrtdog Epic Member 5+ Years 100 Posts

    Cap and coil
  10. dwill3015

    dwill3015 Epic Member 5+ Years ROTM Winner 1000 Posts

    I was wondering but the same symptoms apply and with the OBDII I instantly thought of the same problem. Sorry for the confusion.

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