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Thread: Cold start and dies till warm

  1. #1
    Potential Tuner
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    Nov 2015
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    Cold start and dies till warm

    03 2500HD lq4 block,408 stroker, ls3 heads , gm stage2 cam ,102 throttle body ,42lb injectors now. I had speed inc do first tune set up and ran some what , had 96lb injectors which to big for no turbo/blower ,so got 50lb injectors . took truck to another place had them redo tune said could not set up 50lb injectors at 50 only to 39lb ,when I took truck home ran ok ,next morning would not start just start and die left it , swapped out fuel pump to a stealth 340 ,pressure at 50psi now with the 42lb injectors in , can this be a tune issue ?

  2. #2
    Tuning Addict 5FDP's Avatar
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    To me, yes.

    Find a place/person that can really do it right. Giving you the run around like that second shop is just poor business. If they had a few brain cells they could have trouble shooted and fixed it.
    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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    I would give the 2nd place some credit , the injector and cold start is my problem now ,he did stop by the house to check it out ,but my thinking is the tuning which I do not know much about as of yet

  4. #4
    Senior Tuner mowton's Avatar
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    Fuel pressure and injector data have to be correct or all fueling will be off. You can use precentages to try and get close with the new injectors and fuel pressure. calculate the 2 flow rates and adjust perfrom an across the board MAF/VE change based on the delta percentage from the first setup to the current. Will get you close but would recommend you would need to retune as well.

    Aslo make sure you are using the correct TB scalar for the 102 TB....7400 or so IIRC is about right

    Ed M
    Last edited by mowton; 11-28-2015 at 08:02 AM. Reason: Sorry typo .....6400 s/b 7400
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  5. #5
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    INJECTOR2.jpgINJECTOR.jpg
    These are a snap shot of the injector and rpm ,the injector spikes up then shuts down

  6. #6
    Potential Tuner
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    So installed a new pcm and did a stock tune to it ,and fired right up ,will still need to have everything set up

  7. #7
    That seems like a lot of fuel on startup to me. My 42lb injectors fire at around 3ms on startup and idle around 2.3ms. Have you compared your tune to a stock tune to see how different they are? When I did mine, I went from 23lb to 42lb injectors and and only changed the injector tables. It would fire right up and idle, although a little rich. I was able to adjust idle airflow from there.

    Just a thought, but it might be worth trying to start with a stock setup, minus injector tables, and see what happens.