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Thread: 5.3 Swap lean condition

  1. #1
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    5.3 Swap lean condition

    Hi guys,

    I'm currently fighting a very lean idle on my 5.3 swapped vehicle. The current setup is as follows:

    2003 (I think) 5.3 out of a Silverado 1500 DBW
    Stock GM truck MAF
    Stock GM truck DBW throttle body
    Stock 5.3 truck injectors
    2000 LS1 intake manifold
    228/230 .585 .585 112lsa camshaft
    PAC1218 valve springs
    Long tube headers
    TH350
    3000rpm stall
    It has new o2 sensors, and new plugs. The LTFTs are pegged, although bank 2 sometimes falls back down, only to rise again. The plugs show a very lean condition.

    The vehicle has been swapped and running for about 4 years now, but this spring I did the cam swap. The current tune is a mail order deal. I went that route before I decided to pick up Hp Tuners. Is there anything that stands out to you guys in the tune or log? Hopefully they post, it's my first time uploading something like this.

    This post is in no way blaming the tuner. If anything I probably screwed something up and I'm just overlooking it, but I figured another set of eyes on whats going on could help me.

    Thank you guys!
    Attached Files Attached Files

  2. #2
    Tuning Addict 5FDP's Avatar
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    What is your fuel pressure?

    Did you smoke test for vacuum leaks or exhaust leaks pre-o2 sensor yet?


    Fair warning here, the stock truck injector are too small once you really start tuning it. They will be far past 90-100% duty cycle once you reach wide open throttle tuning. I suggest upgrading them now before you go over everything again to dial in the fueling.

    You will need to purchase a wideband o2 sensor as well, that is the only way to monitor the air fuel ratio in the exhaust so you can properly calibrate the airflow model.


    I would blame the tuner for a poor setup as it sits though for some parts. He/they mirrored the high/low timing curves, that is not a good idea. If the engine were to sense knock/ping it would not be able to pull timing out to try and remove the knock. The low octane table should always have 3-5 degrees less timing throughout to make sure it can do it's job.

    It also seems the tuner before you was trying to compensate for a poor tune by raping the power enrichment table. If you do the math, it's commanding a stupid rich air fuel ratio. And we don't know what he was trying to target to begin with.

    Look at the power enrichment EQ ratio. It's asking for 1.367, so with the math that is 14.68/1.367 = 10.73 commanded AFR. If say he was aiming for 12.5 on the dyno/street with a wideband and had to command fueling that rich to even come close to achieving that, you can see how bad it really is. I can almost bet that if you logged for injector pulse width avg for both banks and took it for a rip you'd be probably in the 110-120% duty cycle, basically hanging the injectors wide open for a long time.


    This was long winded but as you see, it needs some help.
    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
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    Thank you for the help! I'll take the long winded responses anyday!

    I have an AEM UEGO wideband mounted in the car. Before the tune it was super rich at idle, and now it's completely in the other direction with AFRs reading 16-17.5 at idle. Pulling the plugs show the gauge is right, as they're white as ghosts.

    I've gone over it a few times and haven't found any vacuum leaks. I will look again just to make sure.

    Do you think it be easier to start off with a stock 5.3 tune and build off that?

  4. #4
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    Well, I'm running out of things to check. I pulled the intake and checked the gaskets, and they look fine. The only two things pulling vacuum is the power brakes and the transmission. Both are connected to the back of the intake and look fine. The inside of the intake is slightly oily, more so on the driver side, but nothing crazy.

    The clamps on the intake tube are tight, including the ones around the MAF.

    I even pulled the front of the engine apart to make sure I didn't install the cam a tooth off, and everything looks good.

    I'm officially stumped. Am I overlooking something obvious? Where should I look next?

  5. #5
    Tuning Addict 5FDP's Avatar
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    The idea was to make sure you were not fighting another issue before trying to fix the problem within the calibration.

    I wanted to know that you had 58psi of fuel pressure and that you had no vacuum leaks.

    Now that you know it's good on that part you can fix the fueling to get rid of the lean condition. If it was me I'd smack the lower half of the MAF curve with 5% worth of fuel. Go from 0-7000hz, multiply that by 1.05 to add 5%, then click the smooth selection to even it out. Then highlight the entire primary VE table and add 5% to that as well.

    Flash the tune and connect the car to the VCM scanner, use the special function icon and reset the fuel trims. Start it up and watch what the fuel trims do a little while. They are likely to still go a little lean but it shouldn't be +25 on the long term trims anymore. That will get you started and from there you will have to read up on calibrating the MAF and VE with a wideband to get both side of the airflow model in line.
    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.