Please help

Is there any way to adjust the idle down?

My car idles at 920 and I want to lower it to 750(Chilton - Mitsubish Eclipse 90-98). Chilton only lists a procedure for the 95 turbo model. I tried adjusting the butterfly to close more but it only seems to just stick at a certain point(not much further back then it's adjusted to). The idle will go up when I adjust it to be more open...but that's not really what I need to do.

I know that the IAC(Idle Air Controller) is tricking me up here. If there isn't any way to adjust the idle down as is, then would I need an AFC, ITC, Stanalone, or some other gadget to do the job?

95 Eclipse RS : 5 speed
Gude cams : Test pipe : CAI : Dual air horns
incomming - lower strut bars

If you look at the throttle plate, it rests on a black stop thing. You can turn that in and out if you have a Torx T20 bit. It might be T25, I can't remember off the top of my head. If you have it stick out less, your idle may go down a little bit, but overall it should be automatically adjusting.

that's what fuel injection is for.. computer controlled idle, hehe. if you can't get it down by adjusting the butterfly in the TB.. then the only way would be to change the program in the ECU.

>that's what fuel injection is for.. computer controlled
>idle, hehe.

Well, the turbo model is feul injected as well, but you can adjust the idle on them.

>then the only way would be to change
>the program in the ECU.

Are you trying to say that the only way to adjust the idle on the non-turbo model is to reprogram the ECU. Does our computer have an EPROM? If so, is there anyone who can reprogram the EPROM to lower the idle?

The only hint I have been able to find about changing idle is the AEM standalone computer replacement. I downloaded the demo program, and they have a quite a few idle controls/options built into the system. The problem is that I don't want to spend $1400 to lower my idle.

Please help. All I want to do is lower the idle.

95 Eclipse RS : 5 speed
Gude cams : Test pipe : CAI : Dual air horns
incomming - lower strut bars

You don't need any reprogramming or stand-alone computer. Your car is not supposed to idle at 920 when warm. You can expect it to idle high if the engine is cold, or if you have just started it (warm or cold). Otherwise, it should idle lower. 650-750 is certainly within reason. You may have a leak in the intake manifold or throttle body. Check all of the hoses and connections leading to the throttle body. A vacuum leak will raise idle. Otherwise, you may check your IAC.

Remove the IAC connector and probe the IAC with a multi-meter. If it is out of spec, you may want to replace it.


Corbin

'95 ESI-T
HRC+FMIC+ETC...



Gimme fuel...Gimme fire...Gimme that which I desire

The IAC circuits(1-4 and 2-3) both test at 50 ohms. I've checked for vacuum leaks and there don't appear to be any. I forced a vacuum leak at the feul pressure regulator, and I did notice the idle go down(by about 100rpm) but then it almost immediately(3 seconds) works its way back up to 920 with the vacuum still leaking. That's a pretty small leak(1/4 inch O.D. line) and it made up about half of the difference to 750. The interesting thing was how audible it was - very audible for such a small little leak. So I'm pretty sure that I don't have any leaks.

I don't know. The IAC seems to work ok - just on a higher range than it's supposed to. When I start the engine cold, the idle quickly settles to about 1200 rpm. Then as the engine warms, the idle slowly and eventually works its way down to 920. Is a 300 rpm difference between cold and warm idle normal for this engine?

I think I don't trust the IAC. The short version of the war-story is that about 5 years ago i got a 25 on my PCM and the engine wouldn't idle well at all. So I pulled the AIC, jacked it in and out, hooked it back up, and it worked again...at about the same idle I have always had since I bought the car used - just around 1000.

I guess my problem is that I never questioned the idle speed before now. I just put on a set of Gude cams(.376 lift 237 degree) and was rather expecting the car to sound a bit different at idle, but it sounds the same. Don't get me wrong - I love the cams, they work great. But I'd really like to sound like I have em as well, and I think the reason I can't hear em at idle is because it's off by 180-280 rpm.

I think at this point I'm going to replace the IAC....unless someone else can give me a clue to this mystery....anyone?

95 Eclipse RS : 5 speed
Gude cams : Test pipe : CAI : Dual air horns
incomming - lower strut bars

Your idle should definitely change with cams. If they didn't, they must not be too aggressive. My idle with a ported and milled head already sounds like it has cams and is real rough.

Oh - forgot one thing. Thats a nifty little pic of the AIC circuit. It doesn't look like a scan. Where did you get that?

Thanks for helping me out here Corbin.

95 Eclipse RS : 5 speed
Gude cams : Test pipe : CAI : Dual air horns
incomming - lower strut bars

MetalJim: Chiltons is WRONG. Period.

The 4g63, yes, they have a BISS (base idle set screw) which they can manually adjust to set idle airflow. With the 420A, the idle speed is PURELY computer-controled. There is nothing you can do.

The 420A has a computer controlled servo motor that works an idle air valve to hold an RPM level of roughly 800-850RPM. The 4g63 motors can and SHOULD idle at about 750, per thier factory specs. We idle higher. It's not a big deal.

There is nothing you can do to adjust the idle RPM of a 420A powered DSM. Being that is is computer controlled in it
s purest form, it also lends itself to being a bit screwy at times. It will learn to compensate for vaccuum leaks, it will learn to compensate for excessive fuel. It's like that.. Only real advice i can give you, DEAL WITH IT.

My car has idled funny since day one. It happens. Live and learn.

i got a question. I just unplugged my ecu and reset it, now when i start the car and drive around when i take the car out of gear and am rolling to a stop the engine idles high and then after a few seconds it comes down to normal rpm, it does this more when the car is cold and as it warms up it does it less, at normal operating temperatures it barely does it at all.
is this normal?
thanks
james

>is this normal?


YES. That's exactly what i'm saying, it idles odd because it's learning!

i have gude cams as well and my car fluxuates between 700 and 950 all the time...more so when cold obviously but from what i've read, the rpm fluxuation is a normal thing so i wouldn't worry about it.

Thanks for clearing this up for me Dino - I'll deal with it.

Oh, and thanks for the factory service manual download - that should help a bit.

95 Eclipse RS : 5 speed
Gude cams : Test pipe : CAI : Dual air horns
incomming - lower strut bars