fiav blockoff help

[Aproductions]

my car sucks when it is cold and idles like you wouldnt believe but doesnt when warm. anyways what does a fiav delete do and how do i go about doing it? thanks

 

[jeffo]

The last thing I would do if I was having cold start issues would be to block off the FAIV. Its job is to bypass more air when cold to help with cold starts, and bypassing it will just make it even harder.
I can't find the post right now, but one of the guys from RoadRace pretty much debunked the whole "wax pellet" thing with some nice pictures. I suspect that only applies to 1990 TB's, as the newer ones seen to use a simple bimetal thermostatic spring instead. Instead of blocking it off, its actually easier to pop the freeze plug out of the bottom and simply screw the valve in the whole way if you want to defeat it. On both my GVR-4's the FAIV was out of adjustment, raising the idle too much when cold, and taking forever for the idle to settle down when warmed up. Turning the FAIV screw in just a bit would have fixed them both, had I known it then.
I just had one customer who opened his FAIV just to find that the real problem was that the valve was all gunked up, so it was stuck open. He cleaned it out, and then readjusted it by verifying that it opened when cold water was poured on it, and that it closed when scaulding water was poured on instead.
There could be lots of other things causing your hard starting when cold, so I wouldn't be so quick to blame the FAIV. It could be that your fuel pressure is bleeding down overnight, causing you to have to crank it forever to build pressure again. It could be boost leaks that are pulling in unmetered air, leaning you out too much.

 

[okm12346]

^ I agree with you on everything, but the boost leak. Boost leak/unmetered air/ will make it run rich.

I have tried both partial and full block off plates and they both work. The reason I went with full block off was, because my IAC was shot. Yes it cant hold idle at first start up, but after a minute of holding the pedal it sustain itself. It has always started the first time around, but it need to have the pedal pressed a bit otherwise it dies shortly after. Other than that i keep the idle at 1000-1100 for the winter, because of the prothane motor mounts and 800 during the summer. Idle is dead on, no looping or fluctuations.

other than that, I'd recommend changing the TB shaft seals, the BISS seal and the TB gaskets

 

[ramsack]

the fiav i took apart is from a 91 TB. it is the EXACT design as in the picture and if you take out the metal rod that extends you can see white wax down in there. maybe way later on (2g) there is a bi-metal type thing.

 

[jeffo]

Unless I'm not thinking clearly tonight, unmetered air entering the intake will lean you out under vacuum conditions, since the ECU doesn't know about the extra air, so it isn't adding any extra fuel for it. This can especially make it hard starting, since you will be so lean.
BUT, under boost conditions it is just the opposite, as the air is leaking OUT, instead of being sucked into the intake. So, the ECU adds too much fuel, for air that has already been metered by the MAS, but has now escaped. Right?

 

[TSITurbo95]

Ok, so your everyones advice would be to instead of bypass or block off plates, just screw it in all the way so it wont open correct? Will my idle be funkyfied?

 

[JusMX141]

We did the FIAV bypass on my buddy's 2G last year because it was suffering from horrible idle surge.

The result was a car that would not idle at all when cold without sitting in the car and keeping your foot lightly on the accelerator. Once warm, the car idled better than it ever did before. In his eyes, the mod was justifiable considering the warm idle improved drastically (your car is warm much more than it is cold).

 

[JMiller]

I've done the FIAV/ISC block off, when i start my car i have to hold the throttle open so it simulates a "regular" start goes to 2000rpm then i slowly let off until at 1500rpm and hold it there for 1 min and idle is choppy until it warms up and thermal expansion occurs, coolant warms up, all that good stuff. One one to make start up a little easier is to raise your operating temp idle to 1000rpm by turning out the biss.