Blocking IAC on LT1 and re tune

[LS1Racer]

I have blocked the IAC ports in my LT1 throttle body and was wondering the easiest way to get the idle air back through to get the right idle. I was going to adjust the blades out with the adjustment screws and reset the TPS in the ECU to zero. Is this the best way to do it or is their a better way to accomplish this? I am running a FAST XFI 2.0 ECU. Also is their any adjustment to the fuel map necessary in that lower end of the map? I am running AlphaN and sequential mode. Thanks in advance for the help.

[Jeff Niceswanger]

If you have gotten used to a motor with a properly operating IAC, they have a tendency to spoil you. They will maintain and KEEP that idle at setpoint. Not very keen on Fast. You didn't mention if your dealing with a Superstocker or Stocker. Without the IAC the idles are a bit more contrary on the SS camshafts with their low vaacum, but very tunable. Yes, you will need to run the blades open and reset the TPS, especially with the Alpha.The issue you could possibly have is after getting it happy... so it will idle when cold and going into gear nicely (depending on the convertor)..., as it warms up the neutral idle will go higher than most people like. I build advanced tables so timing will be pulled out and or put in to maintain the desired RPM. The Holley has what they call "Idle Spark" to achieve this, but it only will move it 8 degrees one way or the other. I like 14 to do so,and it takes an advanced table. (If this is on a Stocker, you should not have any issues). Maybe someone with Fast knowledge will jump in here and help.

[LS1Racer]

Jeff thanks for the info. Sorry, I forgot to mention it is a Stocker.There is a timing trim table for idle which allows up to 12 degrees adjustment related to target RPM vs Actual RPM. I can adjust with that I believe for temp variations.

[Jeff Niceswanger]

Originally Posted by LS1Racer

Jeff thanks for the info. Sorry, I forgot to mention it is a Stocker.There is a timing trim table for idle which allows up to 12 degrees adjustment related to target RPM vs Actual RPM. I can adjust with that I believe for temp variations.

You should be good. Set your base idol at 20- 22 and let the trim do its thing.

[countrypuppy4865]

You may also have to adjust numbers on the fuel map at idle. Generally adjusting the screw and/or the fuel map at idle you should be able to achieve idle.

[mike britt]

I built an adjustable air bleed to screw in where the IAC goes so I could leave the throttle blade closed at idle.

[Larry Hill]

Might want to check with tech if the IAC adjuster replacement is below the throttle blades. The replacement could be viewed as an adjustable vacuum leak. Sometimes tech thinks a little differently than the racer.