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  1. #1

    Angry 04" Rough Running Problem, baffles me

    My name is Larry Payne, I have a 2004 Silverado with I believe a Vortec 4.8l v-8. When on a trip at highway speed it starting running rough acting like it was starving for or drowning in fuel. When I kicked it down to pass you couldn't see through the black smoke behind me. It has done this a couple of times now and the code reads P0300 (random misfire). I don't know if this has anything to do with it it but the air conditioning also quit working on the drivers side only which makes absolutely no sense to me. I cancelled the code and it hasn't done it since, around town it seems fine.

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  2. #2

    mfleetwood's Avatar
    Join Date
    Jul 2010
    Denver, CO
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    Not sure about the A/C but here is some info regarding your 0300 code just in case it comes back.

    __________________________________________________ ________________________________

    Random/Multiple Cylinder Misfire Detected

    What does that mean?
    Basically this means that the the car's computer has detected that not all of the engine's cylinders are firing properly. A P0300 diagnostic code indicates a random or multiple misfire. If the last digit is a number other than zero, it corresponds to the cylinder number that is misfiring. A P0302 code, for example, would tell you cylinder number two is misfiring. Unfortunately, a P0300 doesn't tell you specifically which cylinder(s) is/are mis-firing, nor why.

    Symptoms may include: the engine may be harder to start the engine may stumble, and/or hesitate; other symptoms may also be present

    A code P0300 may mean that one or more of the following has happened: Faulty spark plugs or wires; Faulty coil (pack); Faulty oxygen sensor(s); Faulty fuel injector(s); Burned exhaust valve; Faulty catalytic converter(s); Stuck/blocked EGR valve / passages; Faulty camshaft position sensor; Defective computer

    Possible Solutions
    If there are no symptoms, the simplest thing to do is to reset the code and see if it comes back. If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors. Random misfires that jump around from one cylinder to another (read: P030x codes) also will set a P0300 code. The underlying cause is often a lean fuel condition, which may be due to a vacuum leak in the intake manifold or unmetered air getting past the airflow sensor, or an EGR valve that is stuck open.

    Mike (Denver, CO) - 2008 Sierra 1500 Z71 SLE 5.3L 4WD

    SUSPENSION: Rancho 4" Suspension Lift; Rancho RS9000XL Shocks; Rancho Skid Plates; Rancho MyRide Wireless Shock Controller;
    BFG All Terrain KO 315/70/17
    DRIVE TRAIN: 4.56 Gears; Detroit TrueTrac Differential; True Cool 40k Transmission Cooler
    PERFORMANCE: DiableSport Predator Tuner; Custom Tuned by Diablew; Magnaflow Exhaust; AFE Cold Air Intake
    ELECTRONICS: Kenwood DNX6180 Touchscreen; Subthump box w/10" Kicker; Driver Information Center (DIC); Rear View Camera
    ACCESSORIES: Westin Brush/Grill Gaurd; Westin Nerf Bars; Truxedo Tonneau; 20% Tint; Tow Mirrors w/Heat & Signals

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  4. #3


    Thanks for the info, it appears by the possible causes, that it might be cheaper to trade it for a horse than try to find the problem

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