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This is a discussion on help within the Computer & Tuning forums, part of the LSx Technical Help Section category; What should the ltft % be on a pretty basic 402 be, mine are reading around 14.5 % at idle ...

  1. #1
    grand poobha james schofield's Avatar
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    tan
    1999 trans am

    help

    What should the ltft % be on a pretty basic 402 be, mine are reading around 14.5 % at idle but when the engine heats up the car doesnt want to fire like its getting to much fuel at start up, so what I have to do to get it to crank is hold the throttle open a little bit to get it to fire, if I dont it will barely run at 200 rpm or so and fluxuates up and down for a few seconds before smoothing out. had my computer tuned by howell engines and the guy that tuned it has no idea of what it could be. im only getting around 200 miles on a tank of fuel and it smells real fumey at idle. any help would be great.

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    Veteran 0rion's Avatar
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    06 duramax

    you really should put a wideband on it to see what the fueling is at idle. What mods do you have and size of cam? I've never heard of howell engines so I can't comment on them but are they experienced with tuning these cars? The fact you can keep it running by cracking the throttle open makes me think it's a tuning issue.

  3. #3
    grand poobha james schofield's Avatar
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    tan
    1999 trans am

    Quote Originally Posted by 0rion View Post
    you really should put a wideband on it to see what the fueling is at idle. What mods do you have and size of cam? I've never heard of howell engines so I can't comment on them but are they experienced with tuning these cars? The fact you can keep it running by cracking the throttle open makes me think it's a tuning issue.
    the mods are 219 227 113 on the cam the heads are ported and polished 90 mm throttle body fast intake 30lb injectors , howell does alot of computer work so i figured it would easy to get them to do it but i guess i was wrong. I think it is getting too much fuel at start up, it acts like a carburated engine thats up to temp and you try choking it during start up , but once you crack the blades open it will fire. and when its cold it busts right off. thats just what I think and the guy that tuned it thinks it needs to be richer ? but im new to this tuning stuff im old fashioned , reading plugs and checking exhaust temp .

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    Veteran 0rion's Avatar
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    06 duramax

    if they aren't experienced with ls1 cars I would be leary about having them tune your car. It sounds like an airflow issue to me.

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