Menu

98 GMC Sierra K1500 Rough Idle

Home Forums Stay Dirty Lounge Service and Repair Questions Answered Here 98 GMC Sierra K1500 Rough Idle

  • Creator
    Topic
  • #665045
    EthanEthan
    Participant

      I have looked on the FAQ page and still can’t seem to find the problem. When I bought the truck it was running really rough, at the site I had diagnosed the #8 cylinder was having issues firing, so new plugs and wires were in order as the original plugs were still being used. Since then they have been replace as well as new upper and lower intake gaskets, crank position sensor as that was the only code that had been read, I also cleaned the spider injector system, everything worked. I have adjusted the distributor forward and back several teeth to find the right one as I can’t get a view of my harmonic balancer with a timing light with the ac compressor in the way. Please help I need to get this on the road but I have done everything I can think of as well as some suggestions from other people with more experience.

    Viewing 6 replies - 1 through 6 (of 6 total)
    • Author
      Replies
    • #665072
      mattmatt
      Participant

        check the fuel pressure and fuel filter

        #665077
        Andrew PhillipsAndrew Phillips
        Participant

          Fuel pressure, as stated above, is a good test to run. How did the plugs look? Also, don’t forget to check mechanicals before hunting a fuel, ignition, or electrical issue. Run a compression test. Make sure there isn’t a valve or piston problem. Check the timing belt deflection, make sure it hasn’t stretched and that the tensioner is good. If the mechanicals aren’t right, no amount of adjusting or cleaning or sensor swapping is going to make it right. Checking mechanicals also includes vacuum leaks. Make sure there aren’t any of those either.

          #665343
          EthanEthan
          Participant

            Could the problem possibly be a broken valve spring?

            #665909
            EthanEthan
            Participant

              So I was checking the valve springs after everything else and I found a severely bent push rod on the intake valve, I was lucky because it came out very easily, seeing how it had a bent that was at least 3/4 of an inch deep. I hope my mistakes will help others so that they do not have to make them as I did, BTW the bent rod was on the #8 cylinder. Thanks for every ones advice.

              #665912
              Andrew PhillipsAndrew Phillips
              Participant

                Awesome, glad you found it. Hopefully everything else is in good shape. That is why it is so important to check the mechanicals before swapping parts.

                [quote=cap269]If the mechanicals aren’t right, no amount of adjusting or cleaning or sensor swapping is going to make it right.[/quote]

                #665980
                EricTheCarGuy 1EricTheCarGuy
                Keymaster

                  Glad you found the problem. Mechanical is so often overlooked. That said, adjusting timing the way you suggested is not a good idea. Timing is very rarely an issue and if it is, it’s often the result of a mechanical issue. Ignition timing really doesn’t change over time. So the next time you’re dealing with a performance issue, I would put ignition timing toward the bottom of the list.

                  Thanks for the updates.

                Viewing 6 replies - 1 through 6 (of 6 total)
                • You must be logged in to reply to this topic.
                Loading…