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98 suburuban hiccups at highway speeds

Discussion in 'Chevy C/K Truck Forum' started by mjh46560, Feb 22, 2014.

  1. mjh46560

    mjh46560 New Member

    Hi guys and gals. I have a 98 'burb that I bought new. I have had a problem for the last 1.5 years in that the truck hesitates or hiccups at highway speeds. It is like it misses one cylinder firing. I have changed the fuel pump, filter, and ran several tanks with injector cleaner thru it. It seems to be getting slowly worse. It is not throwing any codes. I have seen other posts on here about similar problems and the run from a computer reset to a failing tranny. Any more ideas to narrow down my problem with out throwing tons of money at it? Thanks for any help you can give me.
  2. Scott_Anderson

    Scott_Anderson Member 2 Years 100 Posts

    What engine, how many miles, how do the plugs look, have you done a compression test.
    Just trying to get a little more info.
  3. Jamm3r

    Jamm3r Member 1 Year 100 Posts

    If the tranny you will find out soon enough just by driving it....
  4. mjh46560

    mjh46560 New Member

    More info for you all. I had the Tranny serviced just 6 months ago. Engine is a 5.7L, all plugs recently pulled, gapped and look fine. I have not done a compression test. The "hiccupping" doesn't happen constantly, but is intermittently between a few minutes and 30 minutes. It does not matter if I have the cruise control on or off. It doesn't seem to occur when I am pulling a trailer. If I am just driving the truck without a trailer, it only happens on flat level ground at a steady speed, I have not noticed it when I am accelerating or decelerating, climbing or decending a hill.
  5. Scott_Anderson

    Scott_Anderson Member 2 Years 100 Posts

    It almost sounds like a weak zone in the throttle position sensor.
    As you describe the details, the engine runs fine when you are "working" the throttle.

    "It doesn't seem to occur when I am pulling a trailer. If I am just driving the truck without a trailer, it only happens on flat level ground at a steady speed, I have not noticed it when I am accelerating or decelerating, climbing or decending a hill."

    I personally haven't gutted one open to see what is internal to them if it's an optical sensing assy or if it's a mechanical resistance wiper assy.
  6. mjh46560

    mjh46560 New Member

    I had not thought of the TPS switch. I will look into replacing that as I have also noticed the gas pedal sticks occasionally at idle and it have to give it a quick healthy tap to break it free then it works smoothly for awhile.
  7. Conlan Rose

    Conlan Rose Active Member 2 Years 1000 Posts

    If the throttle is getting stuck check to see if the throttle plate is dirty it may be causing it to stick when closed.
  8. mjh46560

    mjh46560 New Member

    Conlan, can you tell me where the throttle plate is?
  9. jsmith4816

    jsmith4816 Member 2 Years 100 Posts

    Odd, I had the same issue when I was drive to and from work on Sunday. I was doing about 60ish and all of a sudden it hiccupped. Thought my tranny went out but I kept rolling. I will have to look into that as well.
  10. Conlan Rose

    Conlan Rose Active Member 2 Years 1000 Posts

    Under the intake resonator on the top of the engine. Its the big butterfly valve that the throttle cable controls in the throttle body. Its hard to miss. Check front and back of it by moving the throttle to WOT and looking at the back side. Also even tho I'm sure your smart enough to know do this all with the engine off.

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