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Thread: 4.3v6 hesitation/random miss/sluggish under load with ac on - 2700-3200 rpm 3rd gear

  1. #1
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    4.3v6 hesitation/random miss/sluggish under load with ac on - 2700-3200 rpm 3rd gear

    ok. i have an 03 s10 4.3 v6, 4l60e automatic. completely stock.

    it has always had this issue:

    between 2700-3200 rpm in 3rd gear under load, with the ac on, i will get hesitation, a random multiple cylinder misfire, and sluggish acceleration for about 10 seconds. once it goes above 3200 rpm, or if i let off throttle and allow it to shift into 4th gear, it goes away and drives fine.

    drives fine in 1st and 2nd gear as well. on even small hills it shifts harshly from 4th to 3rd, or sometimes 4th to 2nd gear. especially with cruise control on. like it doesn't see the throttle change or the load change. again, only with ac on. it can't modulate the cruise/throttle to keep up desired speed, so it slows then really downshifts to catch up. during the 4-2 shifts, it will "hang" at 4500 rpm for 10-15 seconds before upshifting again, unless i turn cruise off.

    ac off, it drives and shifts normally. no hesitation or issues. it's only with the ac on. system is properly charged with correct capacity of refrigerant and works great.

    the following has been replaced (for various reasons) with delphi or ac delco parts.
    fuel injector spider, fuel pump, fuel filter, mass airflow sensor, iat sensor, both front 02 sensors, all cats, plugs, wires, distributor, coil, intake manifold gaskets.

    i've attached the best "printout" of a "log" that i could. i don't have HPTuners yet (going to use it for my LS swapped s10 - different truck) so i can't log with it.

    help or advise?

    i see my 1-2 and 2-3 shifts on the log. it looks like as soon as/right before it shifts into 3rd gear, it pulls massive ignition timing. this is about the 2700 rpm that the problem starts at. it also looks like the calc load drops off tremendously, even though i am still trying to accelerate.
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    Last edited by Cynical 1; 05-17-2019 at 08:50 AM.

  2. #2
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    what are the fuel trims?

  3. #3
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    Quote Originally Posted by GMT800RCSB View Post
    what are the fuel trims?
    LT1 4.7
    LT2 2.3

    ST is usually -1,-2.

    attached are the 02 sensor logs as well during the issue.
    Attached Images Attached Images

  4. #4
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    if you have hp tuners you can log for free with the vcm scanner. it will read codes and will show more data than what you have with the actron. If you connect it run a log and post it people can take a look at it.

  5. #5
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    i have a 2001 4.3 v6 , there sluggish with the ac on , it could be a 3-4 solenoid in the transmission, common problem 4l60e, most time computer doesnt kick the code light

  6. #6
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    Op, did you ever find your misfire solution?