Can't adjust idle low enough

[Mitch41]

Hey guys I have an Evo 1 and i just changed my throttle body shaft seals and my throttle body gasket and biss screw and o-ring, and actually swapped my ISC (my old one was leaking, and I ended up breaking it while trying to get it to stop leaking).
I tested my throttle position sensor with an ohmmeter when I reinstalled. .9k ohms with throttle closed up to 4800 with throttle wide open. Assuming this is good (online said 5k, I'm not sure if it's normal to only get a reading of 4800?).
I did a boost leak test once all of this was together. Held for minutes at 1 bar to 1.3 or 1.4 then would leak out my crankcase vent with any higher pressure (assuming this is rings or valve seals etc).
Grounded diagnostic port (brown plug) and check engine light came on as it is supposed to with our setup. Car was warmed up, screwed BISS screw all the way in and couldn't get idle below 1000 rpm in fixed timing mode.
Any ideas?
My idle at startup is like 1500. Warm is 900 to 1100 dependent.
Car is entirely stock except for apexi intake filter and ported exhaust side, with stock exhaust.
I also noticed the rpm do go up when the rad fan comes on.

 

[kchaazz]

Going by what youve said so far, I have an idea. Do you have the coolant lines hooked to the throttlebody? I ask because its sounding like the fast idle air valve (FIAV) is not closing up properly. The FIAV is what helps give the motor the 1500rpm idle when its cold and first started, which aids in cold starting and warming the motor as quickly as possible.
The coolant lines pass coolant through a compartment surrounding the FIAV within the lower portion of the throttle body, and as the coolant gets hotter, the FIAV closes, thereby dropping idle speed. If you dont have the coolant lines attached, the FIAV will not work properly. If you do have the coolant lines attached to the throttle body, the FIAV can still just be worn out and just isnt closing.
Check this out: http://www.dsmtuners.com/forums/articles-intake-exhaust/320951-fiav-adjustment-disable.html

 

[Mitch41]

Another thing to note is shouldn't the ISC make the idle go to 850 or 750 or whichever anyways? The whole point of adjusting the BISS in fixed timing mode is so that the ISC will always be able to adjust depending on the situation... And never go out of range?
Anyone else have ideas on why my idle would be high even though my BISS is all the way in?

 

[daniel dee]

Going by what youve said so far, I have an idea. Do you have the coolant lines hooked to the throttlebody? I ask because its sounding like the fast idle air valve (FIAV) is not closing up properly. The FIAV is what helps give the motor the 1500rpm idle when its cold and first started, which aids in cold starting and warming the motor as quickly as possible.
The coolant lines pass coolant through a compartment surrounding the FIAV within the lower portion of the throttle body, and as the coolant gets hotter, the FIAV closes, thereby dropping idle speed. If you dont have the coolant lines attached, the FIAV will not work properly. If you do have the coolant lines attached to the throttle body, the FIAV can still just be worn out and just isnt closing.
Check this out: http://www.dsmtuners.com/forums/articles-intake-exhaust/320951-fiav-adjustment-disable.html

x2 ...I believe this is the source of your problems.

 

[cliffkemp]

Just a reply but, I do not have the coolant lines hooked up in one of my cars and it idles at 750 like it should. If the valve is malfunctioning due to being worn out, could be. Sounds like the idle control motor is having issues...

Stumped at the moment on this one...

 

[kchaazz]

The Idle control motor isnt being used at all when youve got both plugs grounded, the motor just becomes "centered" at this point and the ECU relinquishes control of the idle. The BISS should never be in all the way, provided everything else is functioning properly, and if you have no intake tract leaks. Since you have done the boost leak test and have found everything to be sealed, the only two things I can come up with are the FIAV, or perhaps your throttle cable is just a hair too tight and is holding the throttle plate open ever so slightly- it doesnt take much at all to give you troubles. The best way to reset the cable is to loosen the two bolts, then have a friend hold the pedal to the floor while you pull the plate over as tight as you can and tighten the bolts- doing it this way ensures you get the throttle 100% open when you floor the pedal AND the cable has the perfect amount of slack in it when in the closed position so as to allow the throttle plate to close.

 

[Calan]

... perhaps your throttle cable is just a hair too tight and is holding the throttle plate open ever so slightly- it doesnt take much at all to give you troubles.

Or the idle switch is screwed in too far causing the plate to not close.

 

[Mitch41]

Thought I'd update this...
Got my idle fixed while doing unrelated things. Not exactly sure what the problem was at the time.

I am having slight problems. On a warm start, my idle is a bit low and rough for the first minute or so. Then it is proper. Does anyone have any ideas why this would be?