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Thread: Cold start bogging issue

  1. #1
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    Cold start bogging issue

    I have a 5.3 in my Camaro and have recently been experiencing a strange cold start issue. On a cold start the engine is bogging pretty bad when you blip the throttle. If you mash the throttle, or even under a light acceleration in gear, it boggs like a carb'd engine would that is flooded. When I hit the throttle, the RPM drops slightly then very sluggishly begins to climb and seems to catch up to itself around 3k RPM. It does this almost every cold start (its around 70 degrees in my shop), but it has not always done it. I have had the car tuned for about 3 years and it has only been having this issue the past few months. Nothing has changed in the tune, no CEL or codes, no changes to anything. My fuel pressure is rock solid at 60, no voltage drops, etc. I will attach the log showing startup and some throttle blips, and also the tune. I am going to upload a video of it as well and post the link.

    Another issue I have had since day one which I am wondering if anyone has an answer to but is not as important, is it always takes me hitting the key twice to get the engine to fire immediately. If I turn on the key and let the pump build pressure (I have my pump always on with key) and hit the ignition it will turn over a lot and finally stumble to life. If I hit the key for half a second, go back to "on" and then hit the key again it fires immediately with no problems. Again, this issue has been since day 1 and the bogging just started. I just wanted to see if someone could help me out with one, or both issues.

    Thanks!

    03 5.3 W/4.8 pistons T56 MT
    224R texas speed cam
    Holley victor style intake with TB
    Holley 36lb injectors
    no MAF
    Long Tubes
    Attached Files Attached Files

  2. #2
    No Mass Airflow sensor reading....WHY?

  3. #3
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    Quote Originally Posted by LSandlteditor View Post
    No Mass Airflow sensor reading....WHY?

    I know its not the best way to have it tuned but I wanted to keep the cowl hood somewhat appearing original. It has been fine for a couple years and few thousand miles... until recently.
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  4. #4
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    https://youtu.be/Bgm-DCeCenY

    Link to video of startup... This was filmed while the above log was made. I just reconnected the battery not too long before this video so the initial catch in rpm only happens the first start after reconnecting battery.

  5. #5
    So you are running speed density? are o2 sensors working properly? Have you tuned the VE

  6. #6
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    Quote Originally Posted by LSandlteditor View Post
    So you are running speed density? are o2 sensors working properly? Have you tuned the VE
    If the first post is read you will learn that this has been tuned and running fine for the past 2+ years. The VE is tuned. The bogging has recently shown up and looking for someone who can look at my log and tune and see if there?s anything obviously standing out as causing an issue. Thanks

  7. #7
    Tuning Addict 5FDP's Avatar
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    The VE isn't tuned very well just from the looks of it. If you compared it to a stock curve, it looks nothing like it and generally speaking it should. A wideband o2 sensor would be needed to really see how it's running under load.


    Try setting the MAF fail high to 10hz instead of 0hz as a test. The second attempt at starting is what it may be taking to trip the P0103 to start in speed density.

    I'd also zero out all that negative spark in the ETC spark correction table at low coolant temps, you don't need that with this setup. And I'm not familiar with those injectors but if the only thing changed was just the flow rate and nothing else, then that could also lead to issues and incorrect fueling.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

  8. #8
    Well has the weather changed as of late?