Fast idle problem

[Edson Ng]

On cold starts, my fast idle speed is at about 1,700 rpm for a few minutes and then gradually drops down to the 750 normal idle speed. Outside temperature doesn't make any difference. There is no surging at all. I have cleaned the throttle body plus replaced the BISS o-ring which did solve an idle surge problem I had previously. Lowering the fast idle speed using the BISS setting causes the normal idle speed to drop too much and the car will stall easily.

I would appreciate any thoughts on what is causing this and how to fix it. Thanks.

[Marty van den Bosch]

When cold - mine goes to 2000, then to 1500 after 1 minute or 2 then 800 when normal.

I thought that was normal when really cold.

[Edson Ng]

I get 1,700 rpm in the summer and winter.

[Michael Cummings]

edson you dont have anything to worry about because this is what your car is supposed to be doing...this is normal no matter if its summer winter spring whatever.....and marty same thing..thats normal too...when you start your car up in the morning the idle should shoot up around 1500 and then gradually drop to what you have it set at with the biss as it warms up...(normally 750)
so for this little thing you can just take a deep breath and dont worry about it

unless someone of higher dsm knowledge wants to disagree with me

[Michael Cummings]

cleaning the throttle body and doin the o-ring swap with the biss screw were both still good ideas...make everything run smoother

[Edson Ng]

Thanks for the comments Michael. I pursued this because the first fiew times I brought the car to Lowell, he pointed out that the fast idles seems to be higher than normal and turned it down. As I said earlier, this ended up with me stalling in traffic later. After a few unsuccessful attempts, we decide there is no harm with the faster idle so I just live with it.

Just for curiosity, what is the factory fast idle speed?

[Michael Cummings]

i'm not sure that its a factory fast idle speed..i think that the cars just kinda happen to do that and its okay..because i know some that dont do it...but everyone i know there car does the same thing..mine personaly shoots up to around 1500 then drops to 850 (i have my idle set higher because its really rough at 750 without a balance shaft)
i'm sure you already did/know this..but if you want to set the idle bring the car up to running temp then adjust the idle ...dont adjust it when the car is idling at 1500 after startup

[Edson Ng]

Did some more searching. Looks like this could be related to ISC starting to go

http://www.labattz.com/phpBB2/viewtopic.php?t=1694&highlight=fiav

[Travis Merrick]

Have you done any intake work?

Basically I lost my idle when i put my UICP on, like i mean stalling and fumbling everywhere, so I set the BISS to about 900rpm.  My idle starts like this, turn it on goes to 1300 just before it gets warm it drops to 750 then when it is completely warm it goes up to 900rpm and 750 if i put on the rear defrost.  T/E/L + loosing idle = common, we just put up with this stuff, just like that damn squeaky hatch!

[Edson Ng]

I have had the car since new. I think the fast idle used to be in the 1200 rpm range. Then after  about 10 years and the car still completely stock, I got idle surging so I did the throttle body cleaning and BISS o-ring which solved the surging but the high fast idle problem stayed (1700-2000 rpm range). I have since modded the MAS (silencer removed, screw backed out, lower honeycomb removed) and added Dejon UIC. So the fast idle problem is not related to intake mods.

The fast idle process seems to work fine. Starts high, and drops smoothly down to a steady 750. The only problem is that the initial speed is higher than it used to be.

[Michael Cummings]

these are really finickey cars dude you just gotta suck it up and deal with it.....when you go wot..all is lost and forgotten..unless you have fuel cut like me..lol

[Lowell Foo]

I have had the car since new. I think the fast idle used to be in the 1200 rpm range. Then after  about 10 years and the car still completely stock, I got idle surging so I did the throttle body cleaning and BISS o-ring which solved the surging but the high fast idle problem stayed (1700-2000 rpm range). I have since modded the MAS (silencer removed, screw backed out, lower honeycomb removed) and added Dejon UIC. So the fast idle problem is not related to intake mods.

The fast idle process seems to work fine. Starts high, and drops smoothly down to a steady 750. The only problem is that the initial speed is higher than it used to be.

You can adjust the Fast Idle Air Valve by knocking out the frost plug on the throttle body and turning the valve seat with the end of a pair of needle nose pliers until you get the desired cold idle speed.

On cars with the throttle body water lines bypassed you'll need to close off the FIAV completely otherwise it will never go out of fast idle mode.

[Kevin Standeven]

throttle body water lines...would those happen to be (or be included in) the four vac lines on the throttle body facing the front of the car? the ones you would remove if eliminating the emission controls on your car?

[John Hartman]

Kevin, no, they are larger coolant hoses about the size of heater hoses. It comes from your thermostat housing and goes into the throttle body, warms the fiav wax and goes out to the system again.

Lowell, I didnt know you could adjust them oh well, mine was soooo bad(rusted, broken springs, crudded up real bad) I had to block it off completely.

[Kevin Standeven]

phew, thanks John. I didn't think water lines could mean vacuum lines, but there was a twinge of worry regardless...