do these cars ever idle correctly?

[WhiteR/T]

Originally Posted by i3igpete

hunting idle and bucking under load sounds like a big vacuum leak

Mine doesnt buck under load. Only when it is "freewheeling" like not up or down a hill, just that inbetween when the engine is neither pulling or braking. I'm sure its the same with 91rt...

[3Sfever]

If you car is doing the "idle up and down thing", check out the Wiki, an article titled "Idle Problems"
--> http://www.3si.org/wiki/index.php/Idle_Problems

I just added a link I found a while back to a DSM site, and an excerpt from it. This is an excellent description of how the ISC/IAC works, and describes EXACTLY the problem I was having when my ISC/IAC went bad, (idle surge).

Good luck.

[91rtstealth]

yes white r/t..that's exactly what mine does....also, if I let off the gas in 1st and let the car go on it's own, it bucks back and forth...real freaking annoying...for me, and the passenger..hah..mainly for me though..


in addition..the screw you mentioned is the SIS screw I believe...apparently there's another screw called teh BISS screw...at least that's what I understand from looking at other posts about adjusting idle

[91rtstealth]

update on my car

i just removed the apparent "perfectly working" IAC that I got from someone. I plugged it in, turned the key on, and looked at what it was doing....it seemed to be struggling to move...and it was making all kinds of funky noises and motions...so verdict, i'm pretty sure that thing was shot....in addition, it actually looked just a tad bit different than my stock one...the stepper looked longer and he 4 little fins on around it..which leads to another question...do the IAC's different from year to year? My car is a 91..i can't quite picture the stealth he took it from, but I believe it was a 93..but could have been newer...is there any differences? I thought the 95-96 stealth na's were slight diffferent..yes, no?

anyways, so now I am back to my stock IAC situation...bucking in first gear...car falls on it's face unless the idle screw is bumped up...but at least the idle doesn't bounce up and down twice a second like it did with the other IAC...right now it's fairly steady around 700, but sometimes it goes up a little above 1k...and when you give the car gas and let off, the idle drops down real low and comes back up...

a new discovery...after reading through the link about the talon's idle problem that someome posted on here, and stealth316's page..i educated myself about IACs a little bit...

i noticed that my idle doesn't go up, but drops, when I put on all the accesories, or turn the steering wheel..etc...it doesn't do anything when I turn my a/c on cuz i don't have any freon..damn r12...neways, according the most articles i've read, the IAC is supposed to supply more idle when you turns the wheel, or have a large current load on the electrical system...well mine isn't doing anything...

IN ADDITION...i tried unplugging the IAC while the engine was running..and it is supposed to apparently idle around 1500...well, it made no difference what so ever...in fact, with it unplugged...i adjusted the idle screw to see what would happen, and it acted just as if the IAC was plugged in...



all this idle non-sense started last year or so a few weeks after I added a second amplifier in my car..now hold up..don't jusp to conclusions..hah..I originally had a sub with one amp..then I added a second amp for my speakers...and added a capacitor as well...i'd say maybe a week or two later, the car started falling on it's face..so right away I thought "alternator"...disconnected every piece of stereo equipment I put in the car, and it still did it...so whether the car audio stuff is hooked up or not, it will still do it...so I think it was just a coincidence, but who knows with these cars...i had the alt checked..it's perfect...hans at ground zero perfornce bumped the idle up for me just so I could drive the damn thing without it stalling constantly....


can anyone make any sense of all this? are the IAC's different from year to year...no idle adjustment when turning the wheel, cranking up the accesories....connected or disconnected, the IAC doesn't make a difference..etc..i'm going nuts here..

[WhiteR/T]

See this is what I dont understand, mine DOES go up when I turn the wheel or turn on the A/C (he he he, mine works )

[91rtstealth]

well..i don't know what the hell is going on then....i have a feeling i'm just going to have to live with in...and steal an IAC from somewhere..haha..cuz i'm not spending all that money only to find out it doesn't solve my problem..i can't believe how expensive parts are for these old a$$ cars...it's rediculous..

[3Sfever]

It sure sounds like your ISC/IAC is shot.

Originally Posted by 91rtstealth

i noticed that my idle doesn't go up, but drops, when I put on all the accesories, or turn the steering wheel..etc...it doesn't do anything when I turn my a/c on cuz i don't have any freon..damn r12...neways, according the most articles i've read, the IAC is supposed to supply more idle when you turns the wheel, or have a large current load on the electrical system...well mine isn't doing anything.....

Your idle drops when you turn on accessories, and turn steering wheel, etc. because there is more load on the engine. In those conditions the ECU is TRYING to tell the ISC to bump the idle up some, but the ISC is not responding, so the engine slows down because of the load.

The reason it does not slow down when you attempt A/C is because the compressor is not placing load on engine, like it would if working.

Originally Posted by 91rtstealth

IN ADDITION...i tried unplugging the IAC while the engine was running..and it is supposed to apparently idle around 1500...well, it made no difference what so ever...in fact, with it unplugged...i adjusted the idle screw to see what would happen, and it acted just as if the IAC was plugged in...

When you unplug it, the plunger basically just stays where it was positioned when you unplugged it. It does not have a "auto retract" spring or anything.

Not sure if that made sense. I will describe what I did temporarily to mine when the IAC went bad. I pulled the IAC off, ran the plunger all the way out so that it would not allow any bypass air. Then installed it back, but never plugged the harness up. That way it was not going to do anything erratic. I simply adjusted the idle screw to get the idle speed I wanted.

The downside to running it this way is the the ECU can not make corrections when necessary. (like when the extra loads are placed on it). It also idled very slow when hot.

I sure sounds like yours is doing everything mine was. A new IAC fixed it. I hate spending unneccesary money also, but in my case that was the cure.

[3Sfever]

Originally Posted by 91rtstealth

well..i don't know what the hell is going on then....i have a feeling i'm just going to have to live with in...and steal an IAC from somewhere..haha..cuz i'm not spending all that money only to find out it doesn't solve my problem..i can't believe how expensive parts are for these old a$$ cars...it's rediculous..

You can just live with it. I drove mine a long time with the harness unplugged. My A/C does not work either, so it never was an issue, but when the car was hot, lights and heater fan on etc. while idling at a traffic light, the idle would drop to 500 or less. (then the oil light would start to flicker) If you are pushing big amp stereo it might be even worse. You might have to give a little throttle while sitting at lights.

I got tired of driving like that though.

[MustGoFaster]

Originally Posted by 91rtstealth

well..i don't know what the hell is going on then....i have a feeling i'm just going to have to live with in...and steal an IAC from somewhere..haha..cuz i'm not spending all that money only to find out it doesn't solve my problem..i can't believe how expensive parts are for these old a$$ cars...it's rediculous..

You may have only paid $2000-5000 for it but new it was $36K+. Guess what, NEW parts don't depreciate.

[3Sfever]

BTW, if anyone is wondering . . . ISC and IAC is referring to the same thing. That threw me we I was first researching this.

Older documentation seems to refer to this device as ISC (Idle Speed Control?) and newer docs call it a IAC (Idle Air Control?)