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up and down rpm

Discussion in 'Chevy Trucks' started by mdchest, Dec 15, 2002.

  1. mdchest

    mdchest Junior Member
    Messages: 24

    i have a 98 chevy k1500 and i have replaced the fuel filter and fuel pump and the converter and installed a duel turbo exhaust, i have noticed that my rpm's go up and down when im cruising at a steady speed around town, the rpms only go up on tick on the rpm gauge but its very annoying to hear, can anyone tell me what could be causing this? i was thinking that it may be the injectors but it doesnt do this when its idling , it idles perfect( knock on wood) any comments would be greatly apprecitated .
  2. John DiMartino

    John DiMartino PlowSite.com Veteran
    Messages: 2,154

    Sounds like the trans is going into and out of lockup,like it is hunting.Whenever it does it again,lightly ride the brakes as your driving without changing the throttle setting(just enough to light the brake lights),if it stops doing it,then its your lockup torque convertor for sure.This is in the PCM programming,and you may have to go to the dealer and get it reflashed,or if you have put in a Hypertech powerprogrammer,you may need to cal them to have the program changed/adjusted.If thisi snt the problem,id look into the EGR system,the EGR valve will cause the truck to slightly hunt when it opens,it isnt supposed to open until you are going fast enough about 45 so you dont feel it working.
    Last edited: Dec 15, 2002