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Thread: '95 LT1 tip-in Stumble in SD mode?

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  1. #1
    Fuel Injected!
    Join Date
    Sep 2012
    Location
    Huntsville, AL
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    237

    '95 LT1 tip-in Stumble in SD mode?

    Hi guys, I put my '95 LT1 Caprice into speed density mode awhile back to fine-tune the VE tables and ever since I did that, I've had a nasty tip-in stumble from idle. I also disabled PE and DFCO at the same time. I'm attaching a BIN and a Datamaster file.

    I datalogged today and captured the stumble in samples 5350-5550 (toward the end of the run). What I see:
    1. O2 sensors go lean but after RPMs start to climb. Is this due to (normal) delay in the O2 sensor readings?
    2. Spark timing goes to zero degrees (400-600rpm is where the engine is at while stumbling).
    3. EGR appears to be turning on during this time!

    My questions:
    1. Should I add fuel first to the tip-in region of the VE tables and see if that cures it? This is my hunch.
    2. Zero degrees seems low but I suppose at that rpm (400-600) and MAP (96kPa) that's expected?
    3. Should EGR really be coming on this low?

    BTW, my left side O2 sensor occasionally looks lazy off load but then under load it perfectly mirrors the right side. You can see it earlier in the collection. Okay, or need to be replaced?
    Attached Files Attached Files

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