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Thread: cammed 4.3l popping at idle

  1. #1
    Potential Tuner
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    Sep 2018
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    cammed 4.3l popping at idle

    I have 2003 blazer with a 4.3l that I have done some upgrade on. I have added a cam (Comp Cams 56-450-8), valve springs, marine intake manifold, injectors (bosch 0280158165), cat delete, and straight exhaust. I have roughed in the maf and ve table tunes along with updating the injector data. I have a problem with excessive popping coming from the exhaust when at idle or deceleration, but not as frequently. I tried initially swapping the injectors thinking they were the problem, but that didn?t fix it. I found a hole in the y-pipe upstream of the passenger side O2 sensor and fixed that, but same thing. I have attached my current tune and a log file. I am unsure if there is a tune problem or a mechanical issue at this point. Any feedback from someone more experienced with tuning would be greatly appreciated.

    200927-24lb-inj.hpl

    200927-24lb-inj.hpt
    Last edited by knightriderjoe; 09-29-2020 at 06:27 PM.

  2. #2
    Tuning Addict 5FDP's Avatar
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    May 2012
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    The ignition timing is pretty low at idle is some spots because you have two things working against you. You have timing being pulled out because the IAT temps are extremely high for some reason and the timing tables have low timing values in the low rpm/medium cylinder airmass regions.

    Get those IAT temps under control and up the timing is those area's a touch.

    Having no cats is making everything be heard and you won't get away from that unless you put them back in or install more resonators to dampen the exhaust more.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.

  3. #3
    Hard to tell with the log.. most likely a issue with the injector tuning since they are stock injectors.. set that back and start with your ve and maf tuning from scratch as well. you should be needing to remove fuel not add it at idle.

    your fueling is lean because the injectors aren't bigger ..

  4. #4
    Tuner in Training
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    Jan 2021
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    Fayetteville NC
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    did you ever have any luck fixing it? I looked over your log and can definitely say your idle timing dosent look right to me, i have a 2004 4.3 with a mild street cam and i idle at 650-700 at around 18 degrees in park and 25 in drive. in my experiance late timing at idle makes a very loud hum and makes for a weak idle. also the fueling is clearly rich

  5. #5
    Tuner in Training
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    Dec 2015
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    Greensboro, NC
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    Did you degree in the cam? Have you checked your cylinder pressure with a gauge? Good box to check off for your ignition timing.

    Also, another thing to consider is the injection timing with the marine intake and cam. I've playing with this for quite sometime trying to work our similar bugs. Boundry at 5.33 and add a little to the make-up table (.10) until you trims are at their lowest while idling. Then add to the normal table (.10 or so) to help with the tip in.
    My build is a 11:1 4.3 with a 234/240 cam and marine intake.