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Thread: Hoping someone can help me

  1. 01-17-2010 #1
    cresus
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    Hoping someone can help me

    I'm building a kit car that uses an LS1. I've got it all running but when you first go to start it (if PCM has reset) it is very difficult to start. It starts and dies before it finally gets running. After it's run for a while the LT fuel trims max out (+25%) and it'll start up without problem. This indicates a vacuum leak to me but I've looked everywhere and can't find anything. MAP is reading 31kPa which I believe corresponds to around 19" Hg. Fuel pressure is 60 psi. I don't see any exhaust leaks. I have AIR but it's currently turned off so shouldn't be a problem although the hoses could potentially be introducing air to the headers. The MAF was descreened (done by someone else, never run this on a normal MAF) and the MAF is located right behind a cone type filter so could be fairly turbulent. I disconnected the MAF and reset the fuel trims and the car didn't adjust the trims up again but I'm not sure if it will do that when the MAF is disconnected. Still continued to stumble when you blip the throttle. This is literally driving me crazy right now. I can't think of what it could be since I can't find normal ranges for a lot of the LS1 values. Meaning, should my TPS be reading 5% when warm (something like 15% cold start) or should it be 0 and let the IAC control airflow? What is a normal MAP reading? Is 31kPa good, or does that indicate a vacuum leak somewhere? Thanks for anyone's help.
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  2. 01-17-2010 #2
    cresus
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    Yeah, I posted them over in a different thread so I don't have much room left. They're here:

    http://www.hptuners.com/forum/showthread.php?t=27587
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  3. 01-17-2010 #3
    cresus
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    I'm sorry. There's something wrong with me today. From what I can tell it's a stock M6 tune for a Vette. But I haven't looked at all the tables (not sure what I'm looking at all the time yet).
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  4. 01-17-2010 #4
    cresus
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    List of mods:

    Descreened MAF with cone filter immediately ahead of it
    Shorty headers
    No mufflers
    Cats with both fwd and rear O2's.
    Stock throttle body with drive by cable.

    That's it. Mostly stock. I'm hesitant to change any tables from stock since I feel like there's something wrong. With the fuel trims like this I get a lot of popping in the exhaust so seems like a "fake" lean.
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  5. 01-20-2010 #5
    cresus
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    Sorry for the delay. I'm trying to set up the config and am coming up short. I can't find the idle airflow in gear a/c off. I'm assuming that's just the mass air flow output with the car idling and a/c off. Just want to make sure I don't waste your time looking at something when I get it all done. The fact that it's an LS6 tune makes me upset with the guy that flashed it. I had a feeling something like that was happening. I don't have a wideband yet. When I can drive the car I was going to get one to tune the car since the vehicle weight is so much less than the stock vette (2300lbs) and I want to make sure I get it where it needs to be (will also probably end up modding a little more). Thanks again for your help.
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  6. 01-20-2010 #6
    cresus
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    Just out of curiosity, how could you tell it's an LS6 tune? The displacement looks like it's right. Only thing I can quickly see that's different from stock in the tune repository is the VE table.
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  7. 01-20-2010 #7
    cresus
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    Yeah, sorry. That's why I deleted it. I realized when I saved it that I didn't log them correctly. Then I reran and forgot to save it. So...deleted. Also, I tried to edit my tune and got a license error. So yeah, will try again tomorrow.
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  8. 01-21-2010 #8
    cresus
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    Ok. I got the config fixed and rescanned it. One thing I can quickly see is that the IAC looks like it's stuck. Not sure what else means much with the rest.

    I can't scan change the MAF table as I have a VIN/OS conflict that HPTuners doesn't play well with that I have to get fixed.

    Thanks.
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  9. 01-21-2010 #9
    cresus
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    Mostly stock. Base tune is the one up a few posts called original_installed.

    From the way I read this there's a discrepancy in dynamic airflow to MAF output (probably due to incorrect VE table). I'm unclear as to what the STIT is. Since desired is 31g/s and actual is 18 seems like the STIT is decreasing what's called for to keep the idle speed correct (again makes me think there's an intake leak) but it's all new to me.
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  10. 01-25-2010 #10
    69lt1bird
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    Your TPS for the cable operated TB should be a 0% all of the time at idle. The IAC deals with the air needed.
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