FIAV / ISC Discussion Thread

[AdamVR4]

I've read so many threads, full of so much conflicting information...

I've had hot idle surging issues for a while, and just never gave a crap because I'd drive the car on the street just long enough to tune it so I could take it to the track and break it. Probably some sort of disorder. The car doesn't currently run, but it will soon, and while I wait a day for parts to arrive, I figure I might as well look into this...



As far as I can tell, the FIAV works just like a thermostat. The valve expands with temperature (engine coolant) to close an orifice (air passage that bypasses the throttle body).

When you disconnect the coolant lines from the TB, like I did, whether you uncap them or not (I didn't), all you're doing is depriving the FIAV the heat it needs to close the air passage. With that orifice open, it doesn't matter what the ISC does, it cannot control the amount of air that flows around the closed throttle plate. The result? A normal cold-start idle and an uncontrollable idle surging at operating temp. At least, uncontrollable with my primitive e-manage blue (I can adjust timing and fuel).



1G DSM FIAV block off plates do fit our cars. Because JB Weld isn't reversible, I want an FIAV block off plate that retains the ISC. JMFabrications used to sell this exact part. Does anyone today??

*edit* Oh, here it is: http://www.jmfabrications.com/store/...ass-Plate.html

And I ordered the gasket here: http://www.streettunedmotorsports.co...iav_gasket.htm

The only alternative I see is to reconnect the coolant lines to the throttle body and I'd rather do this if I easily can.

Thanks,
Adam

[BigTyla]

The only alternative I see is to reconnect the coolant lines to the throttle body and I'd rather do this if I easily can.

Why would this not be the easiest route? Did you chop off the coolant nipples from the throttle body? From what I'm gathering it appears you just left them on.

I would hook them back up. Why take them off in the first place? What good comes from not having coolant run to your throttle body?

[AdamVR4]

Why would this not be the easiest route? Did you chop off the coolant nipples from the throttle body? From what I'm gathering it appears you just left them on.

I would hook them back up. Why take them off in the first place? What good comes from not having coolant run to your throttle body?

It's for ease of disassembly. If I still can't get the hot idle right, I'll put them back on, but if this works for $30, I'll be pretty happy.

[DrGonzo]

Interested in what you find also. I never run my car in the cold weather so I have no need of the FIAV. I also hate that I have to disconnect coolant lines to remove the throttle body.

[Jimvr4]

The only time I ever removed the TB was to chrome it and change out the shaft seals. It never has to come out when you do plugs.

Also want to mention the FIAV gasket part number is MD614406 so you can buy from Cherry Hill. And - most people aren't going to be able to re-use the 5 phillips screws that hold the housing on. I highly recommend the Lisle 29200 impact driver tool to get those screws off. Once I got mine apart I used socket head screws to put it back together.

[i3igpete]

I've found that with an AEM, I can get idle as low as 600 with the FIAV wide open. I had a combination FIAV/ISC block off plate back when I was running the stock ECU, but it gave me cold start problems.

[green-lantern]

The only time I ever removed the TB was to chrome it and change out the shaft seals. It never has to come out when you do plugs.

Also want to mention the FIAV gasket part number is MD614406 so you can buy from Cherry Hill. And - most people aren't going to be able to re-use the 5 phillips screws that hold the housing on. I highly recommend the Lisle 29200 impact driver tool to get those screws off. Once I got mine apart I used socket head screws to put it back together.

I didn’t have a single bit of trouble removing the screws and reusing them. I just made sure the screwdriver I had fit real well. I assume it’s one of those things where some are easy and some are a bitch.

It doesn’t bother me to remove the hoses, it takes me about 30 seconds with the pinch type clamps and angled pliers. I just stick bolts in the end of the hoses to keep coolant from leaking all over.

Adam, are you using a NA water neck or do you just have them capped off? I’d wait till the issue pops up again then hook up the hoses and see if that helps it.

Edit: It’s the turbos that are fed by the water neck? I can’t remember what feeds the damn throttle body.


Edit: OK it feeds them both. I know some go to the NA water neck but that's so they don't have to cap off the turbo feed lines (when they don't run coolant to turbos).

I had a brain fart there.

http://www.supercar-engineering.com/...e/DSC04104.jpg

[Nihil]

I did an informative post on the other site a long while back about the guts of the FIAV, I took the pics down though, I still have everything on my comp, but it'll take me awhile to get to uploading, yer pic isn't loading up. But yeah, it's just a thermostat type of thing, it looked to me that it could be adjusted too, and possibly have a lower cold start idle, or higher, if desired.

There was a long thread on the other site and there's some info on the DSM forums, but a lot of guys were gettin the FIAV block off plate and keepin the ISC, and adjusting the BISS all the way out (I think it was out) and getting a decent idle and depending on weather and temps, some had some problems while others in warmer climates had none at all...I bought my block off plate from slowboyracing, came with the gasket and new screws, haven't installed it yet...

If you pull that freeze plug out, there's a threaded fitting, I'm takin a guess, you could unthread it, releaving tension on the spring and plunger behind it, thus lowering your cold start idle. I'll have to post up my pics, further more, there is NO wax or anything like that, in there to be ruined by cleaning out...

[AdamVR4]

I've found that with an AEM, I can get idle as low as 600 with the FIAV wide open. I had a combination FIAV/ISC block off plate back when I was running the stock ECU, but it gave me cold start problems.

Right. I read a lot of your posts on the subject last night. It sounded a little annoying to keep the car running while the engine was cold and I'm hoping to avoid that. Did you ever try blocking off the FIAV and retaining the ISC?

[AdamVR4]

The only time I ever removed the TB was to chrome it and change out the shaft seals. It never has to come out when you do plugs.

Also want to mention the FIAV gasket part number is MD614406 so you can buy from Cherry Hill. And - most people aren't going to be able to re-use the 5 phillips screws that hold the housing on. I highly recommend the Lisle 29200 impact driver tool to get those screws off. Once I got mine apart I used socket head screws to put it back together.

I prefer not to break the seal between the TB and the intake manifold if I can help it. I replace my spark plugs a lot more frequently than most people.

I totally agree, an impact driver is a must. I picked one up at harbor freight for ~$5. Of course, the least accessible one had already been pretty much stripped prior to buying the impact driver. I used a chisel to pound a slot into the head then used a large flat head screw driver. Worked like a charm...

So I just ordered this hardware to replace the FIAV and ISC screws. Unfortunately, mcmaster doesn't sell metric SHCS with captive lock washers.

91292A193 1 Pack Metric 18-8 Ss Socket Head Cap Screw M5 Thread, 35mm Length, 0.8mm Pitch
91292A127 1 Pack Metric 18-8 Ss Socket Head Cap Screw M5 Thread, 18mm Length, 0.8mm Pitch
91292A126 1 Pack Metric 18-8 Ss Socket Head Cap Screw M5 Thread, 16mm Length, 0.8mm Pitch (for the ISC)
91111A124 1 Pack 18-8 SS Lock Washer For Socket Head Cap Screw M5 Screw Size, 8.8mm Od, 1.5mm Min Thick
92148A170 1 Pack Metric 18-8 SS Split Lock Washer M5 Screw Size, 9.2mm Od, 1.1mm Min Thick