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Big Jerk

Discussion in 'Engine & Drivetrain' started by sealandsky, Apr 5, 2020.

  1. sealandsky

    sealandsky Full Access Member

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    My last dealer visit was in January so they could damage my dashboard. The visit prior was for them to remove the ECM and send it to Callaway for software update. The vehicle has run great until the last couple weeks when this issue started. I feel the issue is definitely engine related, it will hold RPM's even with my foot off the gas pedal - It's kind of disconcerting.
     
  2. sealandsky

    sealandsky Full Access Member

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    Almost 10K miles btw.
     
  3. sealandsky

    sealandsky Full Access Member

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    I don't have the scan tool, but having one hooked up would be ideal!
     
  4. hcvone

    hcvone Full Access Member

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    Hi Rich, so it ran ok when the computer was retured from Callaway, and then started out of the blue? Have you added any gas dry to the tank? It sounds like bad gas i.e. water in the fuel. Did this happen a day or two after refueling? Does you state have 93 or just 91? Yea I would be pissed, I only have half the miles you do, but not one issue so far
     
  5. wildcatgoal

    wildcatgoal Member

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    Had this on a 2011 Silverado. It would also race RPMs when stopped randomly. Replaced the throttle body. Issue gone.
     
    sealandsky likes this.
  6. sealandsky

    sealandsky Full Access Member

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    Yeah, everything was awesome, running like a champ and then one day it's like my Yukon caught the coronavirus. Slight loss of WOT power (I can feel it in the shifts - Less of a "bang" and more like a stock Yukon) and then of course the surging and jerking mentioned above. I might try some "gas dry" and also will pull off my intake this coming weekend to check the throttle body for gunk. It's time to put in a new air filter anyway...
     
  7. sealandsky

    sealandsky Full Access Member

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    So yesterday I watched as the car accelerated all on it's own (foot off gas pedal) to 1800 rpm in 1st gear, then the rpm's fell back to idle speed and the car shifted to 2nd.
     
  8. sealandsky

    sealandsky Full Access Member

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    And yes - I'm running BP 93 octane and almost always buy it from the same gas station. I might mix it up and find a different one for a couple tanks.
     
  9. sealandsky

    sealandsky Full Access Member

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    I'm following up on my original post and also saying thank you to "Wildcatgoal" who suggested it might have something to do with the throttle body. I finally got some time to dig in to things and decided that the throttle body being dirty was a good bet - In spite of having only 12,000 miles on my Yukon. I bought a can CRC MAF cleaner and also CRC throttle body cleaner and first hosed down the MAF so it could dry for a while while I accessed the throttle body. Once I had a view down the bore I saw a fair amount of black gunk, so suspicions confirmed I removed the throttle body for a good cleaning. Half a can of CRC later aling with rubbing with a rag, toothbrush and finally polished with some very fine steel wool it appeared to be as clean as it could get. I read online that you aren't supposed to move the butterfly as it could mess up the calibration, but if I didn't move it I could not have cleaned it very well. The faint ring around the inlet bore is a machining mark. After reassembling everything I took it for a drive and can say that this solved my problem! This leads me to think that my next purchase needs to be a "catch can" as I'm clearly sucking a whole bunch of crap from my breathers. Or else, every 10K miles I need to do the cleaning.

    IMG_20200522_1439054.jpg IMG_20200522_1439252.jpg IMG_20200522_1454211.jpg IMG_20200522_1454376.jpg
     
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  10. dsh1106

    dsh1106 Member

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    @sealandsky

    Thanks for posting this, I just did this to my 2017 trying to cure some hesitation and low speed drive ability response issues. It appears this maybe the fix, never thought at 24k the throttle body would be this dirty,

    Thanks again
    Scott
     

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