ISC???

so when im driving the VR-4 when im coming to a stop my idle is reving up and down until i come to a complete stop then my idle goes back to 9rpms, how do i test my ISC?

 

Go to vfaq.com and look under intake, its towards the bottom.

 

[HHIVR4]

Try this

Its simple..

 

Is it a "complete stop", or anything below 11mph?
In most cases this is actually not the ISC's fault, it is just outside the ISC's range of control. If you have a logger, see what step it is on when surging. If it is at ZERO, the ISC is already trying its darndest to lower the rpm's. Both my GVR-4's had hyperactive FAIV's, which made it necessary to turn the BISS screw in 1/2 to 1 turn everytime the weather started turning colder. If you live in a cold climate, so need to keep the FAIV, the proper fix is to either replace the FAIV or pop open the freeze plug underneath the FAIV and screw the thermostat in a bit to reduce the effect of it. After 17/18 years the thermostat gets way out of calibration.

 

i have a keydive stage 3 chip and a logger, but i just gt the car and i am not familar with using it, and what is this FAIV yur talking about, im kinda new to this, just trying tolearn everything i can?

 

[turbowop]

If you want to learn, do some reading on www.vfaq.com .

 

The end of the throttlebody where the ISC is bolted on actually has 2 cavities, which do similar things. Both the ISC orifice and the FAIV orifice allow extra air to get bypassed past the throttle blade in the TB, which will raise the idle automatically. The ISC does this as a stepper motor under control of the ECU, which can finetune the idle rpm. The Fast Idle Air Valve does this as a very coarse adjustment based on temperature. It is a simple thermostat spring with an adjustment screw, which is heated by coolant that is looped through that side of the TB. When cold, the FAIV opens the orifice wider, to allow more air to get past the throttle blade, but as the coolant warms up it closes off the orifice and the idle drops. The problem is that as the FAIV spring ages it gets out of adjustment, and opens the orifice too far, even when the temperature outside isn't very cold. This extra air causes the idle to raise so high that the ISC can't pull it down enough, even if the ISC shuts it's orifice completely. At this point the ECU also tries to play with the timing to lower the idle, which causes the surging, if I recall. For years I had to turn the BISS screw in a bit every time the temperature dropped, and then I had to turn it back out when we had a warm spell. After I moved to Florida, I got tired of it, and since I didn't really need the FAIV down here I JB Welded the FAIV shut. Since then I have discovered that you can actually adjust the spring, although I have never personally attempted it.

 

ok so the FAIV is a phillips head of a screwdriver right, bc i messed with that to set the idle arund 1000 rpms at idle, but still when i rll to a stop it will still surg from 1000 to 1400 rpms until i completly stp then it stays around 1000 to 1100. thanx for all the info, i really appreicate all the help.

 

You can NOT use the BISS screw to raise the idle to 1000 rpm! It has to be changed in the ECU code, or the ECU will fight you, causing idle surge. Is your chip set for 1000 rpm?

 

[turbowop]

BTW, that philips screw is the BISS, not the FIAV. /ubbthreads/images/graemlins/rofl.gif

The FIAV screw is located behind the freeze plug in the bottom section of the throttle body.

 

Would it be wise to remove the fiav if it snows in the winter time? I think this is what my problem is or am I going to have to keep adjusting the fiav and bissau with every temp change we get?

 

where on vfaq.com can i get more info on how to use my logger with the keydiver stage 3 chip?

 

[BoostedAWD91]

ur not gonna find any info on vfaq on logging with a keydiver chip

 

then how can i learn how to use it, this is my first turbo car so i am clueless, any help would be great?