Stock FAST throttle body hole size?
11-15-2009, 06:41 PM
#6
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i just spent three months working to get stock-like750rpm idle and startup on a 5.3 head 218/224 on 116 cam ls1. we tried many different hole size and blade adjustments working with hptuners. finally, i went against my logic and welded up the hole and adjusted the blades close to the region where it would just not stick(or slightly open) and gained great startup response, less bucking and the smooth idle. relying on mainly iac control, rather than something as static as a hole and/or opening the blade has given better results. just letting you know what worked for this car.
Last edited by disc0monkey; 11-15-2009 at 09:57 PM.
11-15-2009, 09:00 PM
#7
it idled up to 1200rpm with the hole open, i put a bolt/locknut/loctite in to see if that helped and it would not start and run until i cracked the blade with the set screw
maybe my IAC is going bad...the car still doesn't like to idle sometimes...sometimes it randomly starts surging
maybe my IAC is going bad...the car still doesn't like to idle sometimes...sometimes it randomly starts surging
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11-15-2009, 09:54 PM
#8
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are you resetting the computer each time?
everytime before i started to take the throttle body off for adjustment i just went ahead and pulled the fuses to reset the computer. by the time i had the TB back on the computer was reset. I don't know exactly how far my TB is from being shut but i believe it is very close. I have reason to believe with no hole and blades entirely shut it, the car mentioned previously would idle purely by passage of the iac.
if i were you i would keep the hole closed. adjust the screw so the blades are closed(slight stickiness). with resetting the computer each time. keep opening the adjustment screw 1/8 of a turn.(you have a bigger cam so you'll need the blades opened slightly more than me. until it starts getting worse and back it off 1/8 and you found your sweet spot. obviously let the computer learn the idle after like 3-4 min. turn the car on and off a few times and take it around the block.
this is such a pain in the *** but bite the bullit to get that car to run perfectly and it'll be worth it.
gm sucks for designing the TB so we arent able to adjust the screw while on the car.
carburators +1
everytime before i started to take the throttle body off for adjustment i just went ahead and pulled the fuses to reset the computer. by the time i had the TB back on the computer was reset. I don't know exactly how far my TB is from being shut but i believe it is very close. I have reason to believe with no hole and blades entirely shut it, the car mentioned previously would idle purely by passage of the iac.
if i were you i would keep the hole closed. adjust the screw so the blades are closed(slight stickiness). with resetting the computer each time. keep opening the adjustment screw 1/8 of a turn.(you have a bigger cam so you'll need the blades opened slightly more than me. until it starts getting worse and back it off 1/8 and you found your sweet spot. obviously let the computer learn the idle after like 3-4 min. turn the car on and off a few times and take it around the block.
this is such a pain in the *** but bite the bullit to get that car to run perfectly and it'll be worth it.
gm sucks for designing the TB so we arent able to adjust the screw while on the car.
carburators +1
Last edited by disc0monkey; 11-15-2009 at 10:01 PM.
11-15-2009, 10:01 PM
#9
You can adjust the set screw on the car, but it's a pain in the ***.
Use a 1/4'' drive breaker bar (seriously, they exist) and a torx bit (forget the size) that has some of the end ground off. It fits under the TB just above that roundish part of the water pump.
Use a 1/4'' drive breaker bar (seriously, they exist) and a torx bit (forget the size) that has some of the end ground off. It fits under the TB just above that roundish part of the water pump.
11-17-2009, 08:04 PM
#10
I'll try to pay with it some then. Thing is I had it running great for a while, then 1 day it just decided it wouldn't start and run until I opened the blade up some more. Got it running good again and one night at the track I made 4 passes, on the 5th I had to double foot the brake and throttle to keep it running at the line.
