Engine has a Uniform Fluctuation in RPM

Discussion in 'Chevy C/K Truck Forum' started by xJohnDoe001x, May 9, 2013.

  1. xJohnDoe001x

    xJohnDoe001x New Member

    When I run my engine in park at lightly high RPM it has a regular fluctuation, it does the same at idle but not so regular. I installed a new EGR and EGR valve, I checked the MAP, IAC, TPS and their good. The O2S didnt check out, could it cause this? What else should I check?
    I have a '90 GMC Sierra with a 5.7 TBI with a automatic tranny.
  2. offroadmaine

    offroadmaine New Member

    it is possibly for the 02s to cause the slight variation but unlikely they are more for a "long term" adjustments in the sence that your generally not gonna notice the changes that they are making. now when you say fluctuation is it a miss fire/ the rpms are dropping slightly or are the rpms picking up slightly as in you might have a leaking injector on your tbi and its more noticable when your on the throttle a smidge because your pushing more gas at the injector so the drip coming from it is a little more. so determine if your r's are dropping then picking back up or picking up and then dropping back down then check the issue it leads your to.

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