Idle Problem Options

[Az3g]

Hey all. I posted this in the 3g forum, but knew id have a much more knowledgeable group to work with here. So anyways, I have to keep raising my idle, but the next day it will be back down to putting at 500-600 rpm. I have run out of room to turn it up anymore! so what the hell is going on? is there a bad sensor or something?

[jonbonazza]

Hey all. I posted this in the 3g forum, but knew id have a much more knowledgeable group to work with here. So anyways, I have to keep raising my idle, but the next day it will be back down to putting at 500-600 rpm. I have run out of room to turn it up anymore! so what the hell is going on? is there a bad sensor or something?

How are the threads on the idle screw(s)? Also, There should be a nut on the bottom of one or both (If it has two). Check its condition or if it is even still there. Sometimes they vibrate off.

[Az3g]

How are the threads on the idle screw(s)? Also, There should be a nut on the bottom of one or both (If it has two). Check its condition or if it is even still there. Sometimes they vibrate off.

cool thats a start. I know the threads are good, but Ill inspect for the nut next time I mess with it. thanks.

[EMC 3000gt]

There is never any reason to raise the idle unless you are running extremly aggressive cams.

Your TPS or what ever the 3G cars have is shot.

[Az3g]

I am running an HKS 272/300 cam. I always had the idle adjusted fine. the problem is now that the idle will not stay adjusted. So you think its the TPS? What kind of damage to my wallet is that gonna do?

[jonbonazza]

There is never any reason to raise the idle unless you are running extremly aggressive cams.

Your TPS or what ever the 3G cars have is shot.

The TPS is electronically control and wouldn't cause the idle to "drop" permanently if it was going bad. If it WAS going bad, he would have a very lopy and erratic idle, not a steady low idle.

If it WERE one of the sensors on the TB, the TPS would be my least expected culprit. It would more likely be the ISC or the IAC Valve (if equipted) than the TPS as they have more to do with the idle than the TPS does.

[EMC 3000gt]

If it WERE one of the sensors on the TB, the TPS would be my least expected culprit. It would more likely be the ISC or the IAC Valve (if equipted) than the TPS as they have more to do with the idle than the TPS does.

Thank you I get those mixed up.

[Az3g]

so... ISC or IAC then? what are they, and do you know whats involved in the service of these? Im guessing I need the component(s) new. Is it something that needs done professionaly? I do all my own work, but never run into electrical problems... I supose its time to learn...

[ResidentEvil1987]

Well if its the IAC Valve... (Idle Air Control Valve) Then it shouldn't be to bad to replace that... but it will run you $319.99.... Very expensive part.

[jonbonazza]

so... ISC or IAC then? what are they, and do you know whats involved in the service of these? Im guessing I need the component(s) new. Is it something that needs done professionaly? I do all my own work, but never run into electrical problems... I supose its time to learn...

The ISC is the Idle Speed controller. It is hte main component to the idle system. It keeps the idle steady and in cars that are not equipted with an IAC Valve, also has complete control over idle. Some cars also have what is called an IAC Valve which stands for Idle Air Control Valve. This aids the ISC in in equipped cars by controling how much air is allowed past the throttle plate at idle.

Both of their conditions can be checked with the use of a multi-meter. You will have to check the Hayne's Service manual (The Chilton's Service Manual may also include the numbers, but not sure. Also, the FSM doesn't contain these numbers to my knowledge.) for the correct readings.

If either (or both) is bad, they just unscrew off the TB. Installation cna be a bit tricky if you don't know what youa re doing. For the ISC, make sure you have the rotating piece aligned right or it won't function. You will see what I mean if/when you take it apart. As for the IAC Valve, make sure you get the plunger in right.

[Az3g]

alright. Ive dissesemble and reasembled everything at one point or another. But dont know exactly what everything is. Im sure I'll figure it out. I Have a digital multi meter, so thats good. I cant belaive how expensive the IAC and ISC are. that pisses me off.