Balancing Idle screw and BAC

vrracing · 08-12-2009, 11:29 AM

Car: 90 vert with JDM Tii freshly rebuilt
New TPS
no vacuum leaks
idles perfectly smooth at 750rpm,
all emissions intact
RP down, mid and Bonez cat with Corksport catback
ACT Streetlight flywheel
Rtek1.8 with SAFC Neo

Car will occassionally die when dropping to idle. Have replaced dashpot with brand new one but havent tested yet.

Read Section F2 of the FSM. For setting the idle they only touch the BAC. There is no mentioned for setting the idle screw on the linkage. I have a perfect 750 idle but when installing the dashpot I noticed the idle screw does not touch the linkage plate.

Is there a published procedure for synchronizing the idle screw and the BAC?

Here's my theory. I know the ECU uses the BAC to tune the idle speed by opening a valve in pulses (the duty cycle). I assume the more the BAC screw is open, the more air leaks in during a pulse. So my theory is that I should close the BAC screw all the way down and then use the idle screw to open the butterflies to get an idle of about 700. And then open the BAC screw until the idle comes in a 750.

All with the engine warm and the ISC connected.

Sound about right?

Thanks,

Jim

08-12-2009, 11:29 AM	#1
vrracing Rotating Assembly Join Date: Oct 2008 Location: TX iTrader: (0) Posts: 102 Rep Power: 17	Balancing Idle screw and BAC Car: 90 vert with JDM Tii freshly rebuilt New TPS no vacuum leaks idles perfectly smooth at 750rpm, all emissions intact RP down, mid and Bonez cat with Corksport catback ACT Streetlight flywheel Rtek1.8 with SAFC Neo Car will occassionally die when dropping to idle. Have replaced dashpot with brand new one but havent tested yet. Read Section F2 of the FSM. For setting the idle they only touch the BAC. There is no mentioned for setting the idle screw on the linkage. I have a perfect 750 idle but when installing the dashpot I noticed the idle screw does not touch the linkage plate. Is there a published procedure for synchronizing the idle screw and the BAC? Here's my theory. I know the ECU uses the BAC to tune the idle speed by opening a valve in pulses (the duty cycle). I assume the more the BAC screw is open, the more air leaks in during a pulse. So my theory is that I should close the BAC screw all the way down and then use the idle screw to open the butterflies to get an idle of about 700. And then open the BAC screw until the idle comes in a 750. All with the engine warm and the ISC connected. Sound about right? Thanks, Jim