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Thread: Trying to track down issues with my truck

  1. #1

    Trying to track down issues with my truck

    I just recently picked up a 99 Silverado 2500

    I have noticed it has a rough idle, but general driving it is fine

    today I noticed that it doesn't want to rev above 4000 rpm and at certain points of throttle under load almost feels like it is surging.

    I did a case relearn and took it around the block. Same issue with it not wanting to rev past 4k rpm. However I realized I the VCM scanner running, and it is picking up KR in wot.

    The issue I am trying to track down is the fuel trims. At idle they appeared ok, but in all other locations, both the stft and the ltft went positive by a ton.

    I have already replaced the intake gaskets, and would expect to see positive trims idling and them act normal if it was a vacuum leak

    The previous owner had put on some horrible shop made exhaust and a cai. I used maf cleaned to clean the maf when I had the intake off, troubleshooting my rough idle

    the o2 sensors look like they are switching ok, and I am not getting an cel for those. I did get a random misfire under load today, and a maf performance code when I scanned, but it never even set the light.

    Any thoughts on what I should be looking at next?

  2. #2
    Did you check repository and compare stock file see if anybody mess with the tune?
    2003 5.7 RCSB 224/228 114 60lb MOTORONS LONG TUBE HEADERS CAT DELETE 4L80E 3.73

  3. #3
    I assumed the tune was stock but thats a good point. I will check.

  4. #4
    Advanced Tuner
    Join Date
    Jun 2012
    Posts
    225
    It is probably your maf.

  5. #5
    I was thinking that, I may unplug it, and log and drive around and see what I get

    I was also thinking the cat may be clogged. I know that could be a possible reason it wont rev past 4000 in gear