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Thread: LTFT's staying high

  1. 03-27-2011 #1
    wstidham
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    LTFT's staying high

    About the car.

    2000 z28 around 115k stock bottom end around 15-20k on the heads/cam/springs.
    230/232 595/585 114
    TSP PRC 5.3 stg 2.5 heads
    1 3/4 stainless longtubes, 3in y-pipe dumped magnaflow no cats
    28lb injectors
    ls6 intake
    th400
    3200 n20 converter
    9in w/locker 4.11
    no a/c
    still has a4 tune just deleted trans codes

    At first the car seemed like it had a miss in it but no codes or misfires just getting some knock.

    Hooked up to a wideband(havn't got one permanently on the car and no wideband in the log file attached) and it showed to be deadly lean 16 or 17-1 afr so pulled intake and found two intake gaskets missing half the gasket on the passenger side of the intake, got some new gaskets put it back together and the ltfts don't stay pegged at 25 like they did all the time before but still seem high.

    These problems surfaced after being up all winter and changing from mac mid lengths to the longtubes and having the engine temp sensor come off during a nitrous pass at the track and timing jumped up to around 34* towards the end of the run. I keep the timing low all the time because the car sees a bit of spray.

    Anyone have any thoughts? I'm not a tuner but trying to learn.

    Any input is appreciated.
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  2. 03-27-2011 #2
    2xLS1
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    Your fuel pressure is low. At WOT the airflow looks normal but the narrow band O2s go to < 50mv even with the fuel trims adding 20+% more fuel. Put a gauge on the rail and measure it at idle and WOT. S/B 58psi.
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  3. 03-27-2011 #3
    wstidham
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    it shows 58psi at idle without my hotwire kit hooked up and with the hotwire kit hooked up it shows 65psi. I could maybe rid something up to come inside the car with me to drive it?

    Also forgot to mention that I put a new GS340 in it when I put the hotwire kit on, I took unhooked the hotwire kit because it was fowling plugs out something terrible just driving it around.

    Any thoughts on what could cause the FP to be wacky? accessing the fuel pump isn't an issue as I cut an access panel.
    Last edited by wstidham; 03-27-2011 at 06:33 PM.
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  4. 03-27-2011 #4
    wstidham
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    You are the man, my fuel pressure plummits now when I turn the key over only going to 40ish psi. I bet that hose is busted in the tank, pulling it out now.
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  5. 03-27-2011 #5
    2xLS1
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    Your WOT airflow is .72-.80 g/cyl with a commanded A/F of 11.7:1. With that you should not me seeing NBO2s < 50mv. Your injector duty cycle is high and over 100% for a while but even when it is in the low 90s your O2s are < 100mv. I'm still betting it is a fuel pressure issue. Can you trust the FP gauge you are using? What does the WB show at WOT?
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  6. 03-27-2011 #6
    2xLS1
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    Good. I see you found the problem.
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  7. 03-27-2011 #7
    wstidham
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    I'm trying to get these hoses loose right now, I'm betting the hose is busted or split. I even put in a new one the kit came with.
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  8. 03-27-2011 #8
    wstidham
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    Fixed, just took it for a test drive. The pump had slid off the hose and wouldn't fall off due to the bottom of the bucket.

    man I feel special, I guess I'm gonna start looking for an oem type of fuel pump hose to replace this black piece of rubber hose the pump came with.

    Thanks a bunch I feel better that I was dumb.
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  9. 03-27-2011 #9
    2xLS1
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    Don't feel dumb. I've been doing this a long time.
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  10. 03-27-2011 #10
    wstidham
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    oh I feel dumb. Now to find a proper flexible intank fuel line and t-bolt clamps instead of the rubber hose/worm gear clamps the kit came with.
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  11. 03-27-2011 #11
    wstidham
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    Anyone good with swapping my tune over to an m6 tune so the computer isn't looking for the 4l60e at all? Or should I send it to HPtuners magicians?
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  12. 03-27-2011 #12
    PitchblackC3
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    Send both compatible files to support and they will swap the segments for you.
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  13. 03-27-2011 #13
    2xLS1
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    Quote Originally Posted by PitchblackC3 View Post
    Send both compatible files to support and they will swap the segments for you.
    That will save you from having to license the M6 file. Unless you have a full model year 01 F-body license. If you do then just do a write entire with this file and change the vin to yours. Then copy over your tune.
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  14. 03-27-2011 #14
    wstidham
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    I already sent them an email but thanks I appreciate it.
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  15. 03-27-2011 #15
    260B4U
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    look at goodyear fuel injection line its got some crazy soft inside liner that practly molds itself to the hard line
    2002 Z06-408LQ4 583RWHP 496RWTQ on E85 / 919RWHP 895RWTQ @300 shot
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  16. 03-28-2011 #16
    wstidham
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    starting at frame 3662 area I picked up 3 degrees of knock. Everything else seems like it was much better since the fuel issue fix.

    opinions?

    BTW this was 1st gear and 2nd gear pull. Knock didn't pickup til rpms went down to 4800rpms then carried til I let out.
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  17. 03-28-2011 #17
    wstidham
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    Quote Originally Posted by 260B4U View Post
    look at goodyear fuel injection line its got some crazy soft inside liner that practly molds itself to the hard line

    Thanks but found a place that still sells the stock clear corrigated line like comes from the factory for 5 bucks.
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