Low RPM on cold start up.

[Gabriel Shim]

I've been having this problem ever since my ISC died and I've replaced it. Before, my RPM used to start at around 1500 RPM when the car is cold, now it is starting at 500 RPM. I thought it might of been the ISC and I've changed it again and no changes. What else could it be?

I've checked the FIAS on the TB.  
Replaced the entire TB

Eagle Talon turbo

[John Hartman]

you should probably reset your BISSS.

You have to ground 2 pins once its fully warmed up.  Then set it.  Then shut it down and unground them.

Follow procedure in VFAQ.

[Gabriel Shim]

I have tried to reset the BISS and the probablem still exists?  Any thing else?

[Gabriel Shim]

I've replaced my temp coolant sensor and still the problem exists.  I tested for an air leak and found one by the FPR and sealed it.  The only other air leak is is on the exhaust manifold where my EGT probe is drilled.  I don't think that will cause the Idle to lower on a cold start.

What else could I be checking???  I'm out of ideas......

[KevinBuckham]

Does it help if you back out the BISS 2 or 3 turns?  If the stepper has enough room to open up enough I think you should be close to 1500 RPM immeditately after a cold start.  

Small air leaks on even the intake side shouldn't appreciably modify the original idle speed unless the BISS is set incorrectly.  (At least they have never cause me issues.)

Have you checked the resistance of the coils on the new ISC?  

How is your FIAV?  Is it blocked off, or are there problems with it?  I've never looked inside mine to see how it works, but perhaps it isn't flowing any extra air while cold, but I don't believe it is mostly responsible for the few seconds of high idle when first starting.  (I believe it just keeps the idle a little higher by bypassing a bit more air than "normal" until the coolant heats up.)

[Gabriel Shim]

I've replaced the entire TB and problem still persists.  Therefore, I don't think the FIAV and the BISS is the problem.  The FIAV is not blocked off.