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98 k1500 Bad shudder

Discussion in 'Chevy C/K Truck Forum' started by 06lbz, Jul 26, 2013.

  1. 06lbz

    06lbz New Member

    I am new here and am not sure if this topic has came up before.

    My wife drives a 98 K1500 5.7. It has 125xxx miles on it. It is completely stock besides a k&N filter and flowmaster mufflers.

    We have been dealing with an issue for the past 25XXX miles and can not get it completely solved.

    When going up large hills at highway speeds the truck will start to have a bad shudder and lose power and drop about 20mph. If you keep in it, it throws a check engine light. I have not checked the code in a while but it was throwing misfire cylinder 5.

    We have changed:
    Plugs
    wires
    fuel filter
    cap and rotor
    torque converter
    torque converter lockout solenoid
    Trans filter

    We also have checked for vacuum leaks and have found nothing.

    I'm sure we have replaced other parts just cant think of them.

    After replacing the lockout solenoid, the issue went away for a while but has now returned.

    Let me know if you have any suggestions
    thanks
  2. ChevyBoy2009

    ChevyBoy2009 New Member

    Welcome to GMTC!
  3. MrShorty

    MrShorty Moderator Staff Member 1000 Posts

    How many times have you cleared and checked the code? Does it always come up P0305 or does it sometimes come up other cylinders or general P0300?

    Where the problem shows up while climbing hills, one of my first thoughts is a fuel delivery issue. After climbing, the engine gets starved for fuel and starts to misfire. If you have not yet put a fuel pressure gauge on it, I would do so and see if the fuel pressure is dropping off before it starts to bog/misfire.
  4. 06lbz

    06lbz New Member


    Checked the code yesterday and it was a P0300 multi cylinder misfire. We ended up putting on a new cap and rotor again due to a little corrosion. That cap sure didn't last long. It helped a little but still has a shudder. Next will check fuel pressure.
  5. Psyc0

    Psyc0 New Member


    More likely that it's an ignition malfunction or fuel delivery issue, but DO check the compression on all the cylinders as well.

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