Racing Idle

[white00GT]

The problem I'm having is that I have to cycle the computer about every 6 or so starts. When I reset the computer the car idles perfectly at 850-900 where it should.

After I drive for a while (day or two) or about every 6 or so starts. The car will start up and idle anywhere between 1800-2200.

The only way I can get the car to idle back to normal is to reset the computer. So what is causing this and how can I fix it?

I've checked for air leaks, and don't have any. Any other suggestions or ideas

[explicitone]

Originally posted by white00GT
The problem I'm having is that I have to cycle the computer about every 6 or so starts. When I reset the computer the car idles perfectly at 850-900 where it should.

After I drive for a while (day or two) or about every 6 or so starts. The car will start up and idle anywhere between 1800-2200.

The only way I can get the car to idle back to normal is to reset the computer. So what is causing this and how can I fix it?

I've checked for air leaks, and don't have any. Any other suggestions or ideas

2 things to try

1st it take your IAC valve off and clean it with brake or card cleaner
2nd if you have a K&N filter clean maf wires with elec. contact cleaner

[white00GT]

Ok I pulled my IAC valve off and cleaned it. It didn't seem like it was all that dirty, but I do have a some questions about it.

On the top of the IAC valve there is the little black cap type thing. Well Some how mine popped off or something happened but I can't remember so I just put a cap on the top of it to cap it off.

Should I have done this or should I get another one of those black little cap thingys to put back on it. When I had the IAC valve off I took the plug off that I put on it and blew through it. All it is is just a open little hole. This is one thing that makes me thing I should get another one of those caps because I don't remember the black cap fitting tight, I think I just remember it kinda floating around on the tube

Also, how does it work? looking inside of it you can see what looks to be a plunger of some sort. I tryed to test it by plugging it in and turning the ignition on but not starting the car. You can feel it click like it is going to do something but it acts like it's stuck.

Is it stuck, should it move?

[white00GT]

Alright I did some more research on the IAC. The plunger thingy that moves back and forth does not seal when it is in the closed position. Should it seal or should there be some blow-by?

I cleaned my maf wires, senders, and anything else from the maf to the throttle blades. The idle hasn't started to "race" again,

But now at idle it surges between ~500-1200 it's a very slow rythmic surge probably 3-5sec. at 500 taking about 2-3sec to climb to 1200; then hanges at 1200 for another 3-5sec. before repeating.

[Adam94GT]

I'm just waiting for someone to make an IAC eliminator. That thing is such a pain in the ***.

[xxxBlakexxx]

I had a similar peoblem once, but it was a lot more extreme. I replaced my TPS (Throttle Position Sensor) which I apparently screwed up when replacing my TB. You can get them for about $30 at Pep Boys and they are a pain in the a s s to remove because the screws are locked on. You need a hammer drill to break them loose.

[white00GT]

Stupid IAC.

As far as the eliminator goes I don't think anyone is going to be making one. I tryed disconnecting the hose and sealing the opening....that didn't work; the car wouldn't even run. Even with me working the throttle with my left hand and varying the size of the opening in the IAC with my right.

So I repeat stupid IAC.

[Adam94GT]

The IAC is what I actually believe to be an emissions reducing device. I think sudden opening and closing of the throttle results in extra emissions so the IAC is designed to create a smoother transition between open and closed throttle. Which might also explain why it's so difficult to defeat. You'd think installing an IAC block plate and creating a device to hold the butterfly slightly open would work, but it doesn't.

I think I may have another idea for an IAC "eliminator." What do you think of a gutted IAC but with a restrictor plate between the IAC and throttle body to keep the idle from racing?

Maybe that would be possible, hmmm?

I might consider replacing my TPS as well. Does anyone sell an adjustable TPS? Something with slots instead of round holes to allow more adjustment of the TPS than a factory replacement.

[white00GT]

Originally posted by Adam94GT
I think I may have another idea for an IAC "eliminator." What do you think of a gutted IAC but with a restrictor plate between the IAC and throttle body to keep the idle from racing?

Maybe that would be possible, hmmm?

I might consider replacing my TPS as well. Does anyone sell an adjustable TPS? Something with slots instead of round holes to allow more adjustment of the TPS than a factory replacement.

I'm not sure if the gutted IAC w/restictor would work either. When I was messing with mine I had my father starting the car with me working the throttle and my finger on the IAC.

It was too inconsistent, with me doing everything I could to keep the car running the vacum through the IAC was all over the place.

At idle it was sucking like a vacume, but when I would rev the car to keep it from cutting off the vacum would decrease (natuarly).

If I just pluged the hole; no go, the car would shut off almost as soon as I covered it, but if I just left it as a big gapping hole it wouldn't run either. Thats when I started to vary the size of the opening that I was allowing with my finger. I would have to constantly vary the size acording to RPM. Thats what I think that plunger inside of it does, is vary the amount of flow based on the demand. If that makes any sense.

About the TPS I remember seeing somewhere that somebody had a plate that when inbetween the TPS and the throttle body that allowed you to vary the voltage; I'll look to see if I can find that again and get back to you.

Stupid IAC.

[Snakeman]

make sure all the vacuum hoses are properly attatched and parts installed properly, i.e. IAC. the iac valve lets in a small amount of air to keep the idle steady. without it in place, or with it not functioning, you will have the roller-coaster idle. to pinpoint vacuum leaks, try using carb cleaner sprayed around suspect hoses to see if the idle changes.

did you do any recent mods that might have caused it?

[white00GT]

Good news and Bad news; I just did a couple of different things and I cured my idle problem. Although I haven't been able to cure the idleing at ~1800-2100 every 7 or so starts.

Originally posted by Snakeman
Make sure all the vacuum hoses are properly attatched and parts installed properly, i.e. IAC. the iac valve lets in a small amount of air to keep the idle steady. without it in place, or with it not functioning, you will have the roller-coaster idle. to pinpoint vacuum leaks, try using carb cleaner sprayed around suspect hoses to see if the idle changes.

did you do any recent mods that might have caused it?

Your right I just swapped my IAC valve, and it cured the rolling idle. I got a new one for two reasons; mine was hanging because of the carbon, and also most importantly the little black cap that is on top of it, I was mssing.

That little black cap popped off of mine at the track about a month or so ago. Seems like I pulled on the fuel line and it popped off or something like that.

I couldn't find it so I put a rubber nipple ontop of the brass tube to stop the air leak. It turns out the black cap is some type of vent or beather or something; not quite sure.

After switching the IAC valve, and moving the idle to 1000-1050 the rolling idle is gone. But this steady elevated idle ~1800-2200 every 7-8 starts still presist.

Checked for air leaks have none.

Any thoughts?

[white00GT]

umm the only mods I done resently would be that I've switched to Total Seal rings.

I also switched springs b/c I broke one of the Mod Max pieces of.

I think the name of the springs I have now are Duramax or something like that. They are the springs that were at the SEMA show. I've got the box at my house I'll look when I get there. I'm not at home now.

[Snakeman]

*only*
i like that!


so, the motor was just out of the car, re-ringed, and now that it's back in you are having issues?

did you do the overhaul yourself or have someone else do it?

if a shop did it, take it back and make them fix it.

[white00GT]

I was wrong the springs are Endura-Tech springs.

The car has been having th idle issue sense I lost that black cap on the IAC vavle.

Tonight when I cranked up to come home it hung for a sec. at 1300-1400 but then dropped right down to 1000-1050. Once I got to my house after a 20 min drive; put the car in park the idle rose to 1400-1500 hung for about 3-4 sec and then dropped to 1000, and idled perfectly.

I'm not too sure if it's going to start that high idle thing again or not. I'll know for sure tomorrow though.

[white00GT]

I had the idle problem before I took the motor out.

[xxxBlakexxx]

Do you guys use clamps on your vacuum hoses?

[white00GT]

I use worm? clamps on mine

[white00GT]

Ok here we go; the car is still doing the elivated idle at 2200. Today when I got home, I could tell that the car was starting to to do it because it started to idle at 1500 with the car in gear under no load.

Just for sh*ts and giggles I tried to lower the idle using the idle set screw w/the car idleing at 2200 in park. I took the idle screw all the way out of the throttle body, and even pushed on the throttle bracket with my thumb to make sure it couldn't close any farther. The ilde still stayed at 2200.

Needless to say I am now cycleing the computer again to try and figure this idle problem out.

HELP!!!!