My idle seems to be very high, I thought the reference was 1000rpm +/- 100 but it seems I was way off the mark. My car sits around 1300rpm in Neutral, and about 1000rpm in drive. I've referred to this thread http://www.aussiemagna.com/forums/showthread.php?t=31580&page=1 which is about cleaning the throttle body, but at the end states


While cleaning disconnect battery. when all has been re assembled hold foot on acc to floor, turn ignition to on without starting and hold here for 30 seconds. this will reset isc motor.

This seems fairly straight forward, i'm assuming 'reconnect battery' should be included with reassembly? So battery back on, key to 'on' position, hold throttle all the way down for 30 seconds then release?

However....


Start car and bring up to operating temp. stop engine and bridge wire in engine bay behind left strut tower, is usually a beige one but check if unsure. this will turn off the isc. Mitsubishi states idle should be 700 in neutral but I have found it is better at around 850. Only use air screw to adjust as the throttle stop screw should never be touched. (hint, on some models this plug is in different places, fine someone who can show you the right plug and ALWAYS us a fused bridge wire)

The above probably makes perfect sense to somebody's who's done this before. But makes absolutely no sense to me because there's key information missing here. A picture would help immensely
There's about 10 wires behind the strut tower

http://i60.tinypic.com/117uyds.jpg

The only 'beige' one is the plug at the bottom of the picture. But if one is to bridge it, to where? I'm assuming itself since it has 2 wires, but there's 2 ends to this equation. A male, and a female side. Does one bridge the female side (top half), male side (bottom half), or both simultaneously?
And the fuse well... 10 amp fuse?


For the heck of it I tried screwing the air screw in by myself. I got 3 turns in till it was fully seated, idle was still 1000rpm in neutral.
And just to be 100% sure, this is the correct screw right?
http://i59.tinypic.com/dbintg.jpg

The link you put up refers to the second gen, you have a third gen - so ignore that thread and anything it tells you to do. lol

Idle speed is set by the ECU controlling the ISC. No user adjustment of idle is possible, unless you have a MUT 2 gadget.

Put the "idle air screw" back where it was, check for air leaks between the MAF and engine, and replace the ISC.

I've previously checked for leaks by spraying water all over the intake area, no change in idle speed at all

So assuming there are no leaks, how do I check the ISC is working correctly? revs do drop then raise when I turn the A/C on/off

how do I check the ISC is working correctly?

Multimeter. Pull the plug off the ISC, you will see two rows of 3 connections. Measure from the centre of each row to the two outside pins. Note the 4 readings down. If one of them is not like the others, the ISC is kaput.

The ISC is a stepper motor capable of small steps, it opens or closes an air passage under direction of the ECU. If one of the 4 coils is open circuit, the nose of the ISC will be fully extended (= low idle) or fully retracted (= high idle), and unable to respond to signals from the ECU to move in the other direction.

If the ISC is OK, check the throttle stop screw and that the butterfly in the throttle body is free to close properly, might be something simple like the throttle cable is too tight.

PS. Why is there a cable tie around the TPS plug?

Cause it's been cracked and slightly missing one of the corners so it no longer clicks into position. I've run it without the cable tie just fine and it doesn't come out on its own but why not add it?

So what is the idle air screw then? on a carby it controls the mixture, typically air screws are for 2 strokes and fuel screws for 4 strokes.
I presume its a failsafe to mechanically limit the amount of air that can bypass the throttle plate. But err.. isn't that what the ISC does as well?

Simple!
You use the MUT 2 device to switch off the ISC, use that screw to get the idle where you want it, switch ISC back on, and the ECU accepts the new idle setting. ISC will now do it's stepping business to retain that idle under all conditions.

Without using the MUT 2 the ECU will just use the ISC to regain the preprogrammed idle setting, if it can.

(Beginner mistake here: "Carby car have a big screw to set idle speed, this fuel injected car has a big screw, so it must be for idle setting.")

Life is NOT that simple! lol

ISC connectors are arranged
1 - 2 - 3
4 - 5 - 6

I measured 2-1, 2-3, 5-4, 5-6. All of them 39.3 ohms except 5-4 which is 39.9, bugger all difference. So I assume thats fine
I'm pulling off all vacuum hoses and manually blowing through while blocking 1 end, havn't found any leaks so far.
There's a hose which comes off a large black canister (near left strut town) and goes into a filter, then into the top of the throttle body (runs horizontally). I pulled it off and noticed the filter only allows air one way, and that is from the black canister into the throttle body. That correct?

edit: Nope, sprayed 2 bottles of water everywhere where there's an intake hose, no change in revs
Car did settle down to about 1000rpm after it warmed up. When starting cold it seems to start off at 2000rpm and slowly drop to just under 1300rpm
I know i'm going against your advise here but I took the air screw back to 3 turns out (where it was) and then turned it in 1/2 a turn. It now seems to sit around 800rpm when hot (A/C / fans off), turning it in further doesn't change rpm at all. So I might leave it there for a bit and see how it goes
Another question though, is do these engines have a tendency to hang in the idle? If I stab the accelerator it drifts back to about 1200rpm then slowly drops further. I'll post a video later on

Well I pulled the part of the manifold off that houses the butterfly valve. From there I removed the ISC motor and idle air screw. ISC had a bit of crud on it but not a lot, I cleaned it out with some carb cleaner anyway. Then reinstalled the O-Ring it sits against with some new rubber grease on it. Noticed the air screw had quite a bit of crap in there, gave it a good clean out. Also cleaned the edges of the butterfly valve again, pretty clean already though
Then did the very scientific method of holding the housing upside down with the throttle closed and spraying the top of the butterfly valve with some carb cleaner. It's not a perfect seal, it slowly drips a little bit of fluid through so I decided to play with the throttle stop screw. I can't get the butterfly valve to have a perfect seal, but I screwed it out, then back in until fluid started to drip a bit faster, then back out again and used a feeler gauge to try and narrow it down. Looks like I have it about 1/8th turn out from where it was.

Upon reassembly I noticed it's ever-so-slightly sticky when opening throttle from dead closed. So may need to take it in another 1/16th turn. But immediately it's much better at idling and returning to idle.

Before:

http://tinypic.com/r/o8tert/8

After:

http://tinypic.com/r/33f9cfa/8

Revs drop much quicker, after running it for a while it sat almost bang on 750rpm in neutral with A/C off. 800rpm with A/C on and the ISC motor seems to respond a bit faster. Idle screw is also more responsive in that I can screw it all the way in and the car just about dies but the ISC takes over to bring it back up. Before I could have it all the way seated and it would still be around 1000rpm without dropping much. Took it back out to 3 turns

Max, yes but also no, the MUTT does NOT turn off the ISC

What you do is hook up any scan tool which will read the steps on the idle motor, you then adjust the stepper to get it around the 28 steps mark, each time you move the screw it will take a few minutes for the idle to adjust back with the ISC and then you re check and adjust again if needed

I don't have a scan tool so i'm just using whats available to me. Now that i've cleaned everything out, it seems to take less than 5 seconds for the computer to compensate when I turn the air screw and bring it back to whatever revs it wants
I'd like to know a bit more about whats going on. At the moment it seems to me that the air screw is somewhat pointless if the ISC can overrule it and set whatever idle speed it wants. Is it there for redundancy if the ISC fails?
With a correctly operating ISC and ECU I don't see what function it has. Or if there's any negatives to playing with it, it seems to me that it would make no difference winding it all the way in or out

Max, yes but also no, the MUTT does NOT turn off the ISC

What you do is hook up any scan tool which will read the steps on the idle motor, you then adjust the stepper to get it around the 28 steps mark, each time you move the screw it will take a few minutes for the idle to adjust back with the ISC and then you re check and adjust again if needed

Thanks for the clarification, I was trying to interpret what is in the manual, seeing I have no practical experience on the topic.
I'm assuming the 28 step mark puts the ISC in the middle of its range of movement? With the use of the MUTT, is it possible to raise the base idle by say 100 rpm, or is the hot & no load rpm level hard coded in the ECU? (Which implies some ECU recoding is needed if you wanted a hot engine to idle up a bit).

Millenium 7: I imagine the air screw is used in the factory to set the hot idle speed to the 28 steps mentioned above, so that the ISC is in its correct operating state, ie it can wind out to allow more air in when the engine is idling and under load, when you turn on lights, aircon, turn the steering wheel while stationary, etc. You are quite right, the air screw appears to do nothing because the ISC adjusts quickly.

With the use of the MUTT, is it possible to raise the base idle by say 100 rpm, or is the hot & no load rpm level hard coded in the ECU? (Which implies some ECU recoding is needed if you wanted a hot engine to idle up a bit).
Idle target revs for varying coolant temps and load conditions are hardcoded in the ECU ROM. With access to reflashing equipment these values can be easily adjusted.

The air screw is set at the factory to compenstate for minor differences in the parts tollerances and assembley of each engine. It should never have to be adjusted once set correctly. If adjusting it solves a problem then your problem is somewhere else and you are only masking it.

You can adjust it properly by hooking the ECU to you laptop and using Evoscan. It has a command for adjusting base idle that sets the isc in a certain position then you adjust the screw untill the engine is idling at 700rpm. This must be done on a warmed up engine.

My isc motor died,i pinch another from an 2004 Model and it idle properly again my only problem is when the engine is running the throttle slightly stick when first pressed,so my question is to you brilliant minds out there what can i do to solve this issue :)

Could be the throttle plate stop screw. If the screw is turned too far out then the throttle plate can briefly get jammed, as its allowed to rotate too far closed and wedges itself against the throttle body housing. I had this problem with mine, the very first press on the throttle it took a bit extra force on the throttle before it freed up, then it was fine. I just screwed the throttle stop screw in 1/4th of a turn and that freed it up

You can check if thats it by turning the engine off, open the bonnet, rotate the throttle plate / butterfly valve by hand (where the throttle cable connects) if it's already sticky then you know its the problem. Otherwise quickly let it go, allowing it to snap back hard and repeat a couple times If there's any 'stickiness' at all when first trying to rotate the throttle plate, then you need to wind the throttle stop screw in a little. There's an 8mm nut securing it in place, Put flathead screwdriver in the stop screw, then loosen the nut with an 8mm spanner, turn the screw in 1/8th of a turn then tighten the 8mm nut again, repeat test until its allowed to snap back and be operated freely

Could be the throttle plate stop screw. If the screw is turned too far out then the throttle plate can briefly get jammed, as its allowed to rotate too far closed and wedges itself against the throttle body housing. I had this problem with mine, the very first press on the throttle it took a bit extra force on the throttle before it freed up, then it was fine. I just screwed the throttle stop screw in 1/4th of a turn and that freed it up

You can check if thats it by turning the engine off, open the bonnet, rotate the throttle plate / butterfly valve by hand (where the throttle cable connects) if it's already sticky then you know its the problem. Otherwise quickly let it go, allowing it to snap back hard and repeat a couple times If there's any 'stickiness' at all when first trying to rotate the throttle plate, then you need to wind the throttle stop screw in a little. There's an 8mm nut securing it in place, Put flathead screwdriver in the stop screw, then loosen the nut with an 8mm spanner, turn the screw in 1/8th of a turn then tighten the 8mm nut again, repeat test until its allowed to snap back and be operated freely

Thank you so much Milly i will have a crack and report back :) where abouts is the stop screw,is it the one placed on top of throttle body can you mail me a pic please :) jrxbox2005@hotmail.com

Open the bonnet and stand on the front left side of the vehicle. Look at where your throttle cables goes to, thats the throttle plate, you can push it from this side by hand and it'll rotate. You'll see a screw with a flat notch in it, the throttle plate hits against this screw when its at rest, to prevent it from rotating back too far. The screw is horizontal and is in the east-west orientation

http://i62.tinypic.com/b4dhcl.jpg

Circled in red

Awesome thanks :)

Quick update guys suggestion from Millenium7 help to sort this one out,i didn't end up touching the screw this is what i did,( Millenium7 )Otherwise quickly let it go, allowing it to snap back hard and repeat a couple times.
Thanks guys for all the help :)

Quick update guys suggestion from Millenium7 help to sort this one out,i didn't end up touching the screw this is what i did,( Millenium7 )Otherwise quickly let it go, allowing it to snap back hard and repeat a couple times.
Thanks guys for all the help :)

If that free'd it up then you should be touching the screw. Note that mine only ever got 'sticky' once parked overnight and left to cool down. The throttle body contracts very slightly as it cools and binds up the butterfly valve. However once its moved it frees up, or when it gets some heat in to it everything expands a little so there's more tolerance. Thus you want to turn the screw in just a bit (1/8th of a turn at a time) so that it won't bind up in any condition. Excluding maybe temperatures in Antarctica

Hey Millen :) i haven't had any issue since i did that thing so ill just leave for now :)