Correct with the line pinched you will have no power brakes. You don't lose braking power itself, just requires more pedal effort.
And for the timing ground connector, yes you wanna ground the pin in there to the chassis. I'll say it again though, grounding that connector and blindly adjusting the BISS is not gonna get you the desired results. You may be able to get the car to idle better than it is though, it's just not gonna be perfect.

ok im just gonna replace the gasket tomorrow, boost leak test it again and then try to set the idle. ill try pinching off the vac line to the booster just at idle to see if the hunting will stop. ill also replace my throttle body with the one i have the fiav blocked off on. ill keep you guys posted, and again thanks for all the help, it is much appreciated!

91talonts1 said:

Correct with the line pinched you will have no power brakes. You don't lose braking power itself, just requires more pedal effort.
And for the timing ground connector, yes you wanna ground the pin in there to the chassis. I'll say it again though, grounding that connector and blindly adjusting the BISS is not gonna get you the desired results. You may be able to get the car to idle better than it is though, it's just not gonna be perfect.

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I disagree here. There's zero need to see ISC position to set the biss screw. Grounding the idle connector locks the ISC in the middle of it's range. That way it can adjust up or down once* idle is set where you want it. With it locked in the center, you adjust idle to the target idle set in the computer on a car without link is 750RPM +/- 50RPM at operating temp. From there unlock the ISC and it will make minor changes to get it where it needs to be.

Too many people are set on needing 30steps for ISC at idle and 140 for base idle adjust. The computer will alter that reading if it doesn't like it anyways, as long as it has room to open or close to compensate for changes it's perfectly fine

Tyeler18 said:

I disagree here. There's zero need to see ISC position to set the biss screw. Grounding the idle connector locks the ISC in the middle of it's range. That way it can adjust up or down once* idle is set where you want it. With it locked in the center, you adjust idle to the target idle set in the computer on a car without link is 750RPM +/- 50RPM at operating temp. From there unlock the ISC and it will make minor changes to get it where it needs to be.

Too many people are set on needing 30steps for ISC at idle and 140 for base idle adjust. The computer will alter that reading if it doesn't like it anyways, as long as it has room to open or close to compensate for changes it's perfectly fine

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Well you're entitled to your opinion and way of doing things, but I'm gonna disagree with you on a few things too.
First I don't know what an idle connector is. The plug we have been discussing is the timing ground pin, it does not lock the ISC when it is grounded.
There is however a diagnostic pin (on a 2g don't know about 1g) that does lock the ISC. It does not lock the ISC in the middle of it's range though, it locks it at about 9-10 steps.
The reason to shoot for an ISCpos of 30, is because this represents the point the ISC is about a quarter of the way open. The ECU is gonna need it to open it a whole lot more than close it when you're at the desired idle speed, this is why it's ideal to be there. A little room to close and alot to open.
Perhaps too many people do get hung up on it, and yes you can get lucky and get a car to idle fine million other ways too. Many of us have ran without ISCs entirely.

91talonts1 said:

Well you're entitled to you're opinion and way of doing things, but I'm gonna disagree with you on a few things too.
First I don't know what an idle connector is. The plug we have been discussing is the timing ground pin, it does not lock the ISC when it is grounded.
There is however a diagnostic pin (on a 2g don't know about 1g) that does lock the ISC. It does not lock the ISC in the middle of it's range though, it locks it at about 9-10 steps.
The reason to shoot for an ISCpos of 30, is because this represents the point the ISC is about a quarter of the way open. The ECU is gonna need it to open it a whole lot more than close it when you're at the desired idle speed, this is why it's ideal to be there. A little room to close and alot to open.
Perhaps too many people do get hung up on it, and yes you can get lucky and get a car to idle fine million other ways too. Many of us have ran without ISCs entirely. I don't think we should get to caught u

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1g's do have a diagnostic pin to lock the ISC as well as 2g's, while most use a scantool or link to do it which is the proper way. You guys can fiddle f*** around with the BISS all you want, the whole purpose of locking the ISC is to prevent it from fighting you when adjusting, which is exactly why the FSM wants the timing and ISC locked when adjusting base idle because that's exactly what the computer wants. Locking the ISC puts it right where the computer wants it in its range (I use centering loosely), so when you adjust the biss you force it to idle at target idle when you unlock the ISC, it no longer needs to move more than a few steps, because it's already at target. Not dicking around trying to cycle while you're operating the BISS. It's the way Mitsu wanted it adjusted, and it's by far the fastest. The computer doesn't care what ISC position it's at, as long as it's at target idle RPM. I realize not all setups are perfect, vacuum leaks, FIAV out of adjustment, cams and coolant temp even play a roll, that's why trying to reach a target ISC position leaves you waiting 10 minutes every time you make an adjustment, hoping the computer isn't fighting you with the ISC.

Locking the ISC doesn't necessarily put it right where the ECU wants it though. It puts it almost shut more or less taking it out of the equation. Another thing to note is the value ISCpos is not physically where the ISC is. It's the position the ECU has commanded, the ECU controls it like a fuel trim and just assumes the ISC motor is where it told it to be. Viewing ISCpos is also helpful in determining if you have a dead ISC or faulty ECU driver, which is all to common nowadays.

I'm not sure why you want to argue about the whole ISC thing here though. I told the OP adjusting the BISS without a logger may very well improve his idle. I just said doing it that way is not going to achieve the best results. And all you said is ground an idle connector, that doesn't exist so not very helpful. You made it sound like the timing ground pin was the same thing. Maybe you can tell the OP how to ground the diagnostic pin?
The way I use is what I've seen recommended by countless DSMwisemen and the guys who know more about the DSM ECU in the real world than anyone else.

ok so i just got my gasket in, im gonna throw it on and boost leak test the car, i noticed last night when i took it for a cruise that the idle only gets really high when the car is warmed up. so i connected my ghetto logger while idleing at 1800 rpms and it showed my tps% at 6.7. i poped the hood and pushed the wheel on the throttle body towards the battery, and it rotated very very slightly, and my idle dropped down to about 900rpms. is it possable that when my engine bay gets hot, my throttle cable is expanding and pulling the throttle plate opened just a hair causing my eradic idle? i read that if the ecm doesnt see the throttle position at 0% or 1 it doesnt read the throttle plate as closed?

hey there crappy your having all these issue nothing like a bad day with your dsm. I'm not going to say that I'm a full blown expert but your tps sound swing from 0% to 100% my thinking may be that you have a mis adjusted throttle cable. have you done any work in the engine bay recently tried to pull the idle up with the throttle cable its self? first this id do and it seems like you working back words but hear me out. if you go into the cab see if there is excessive play in your pedal that will give you an idea if you have to much play in your cable. next go to your throttle and see how much slack is in your cable to throttle body you don't want to much but you don't want it tight light a guitar string either you need like a happy medium. next your want to make sure the throttle plate isn't getting hung open by carbon or dirt so what id do well you have the throttle accessible is spray and clean the butterfly valve or plate. make sure she freely shuts with the throttle cable loose. Now your want to make sure the throttle doesn't stick give it a couple flicks manually and watch it. if it feels like its sucks your going to want to take a look at your idle switch pin. not sure if your running a 2g or a 1 g. with a 1g your want to check that when the throttle closes that you have continuity between the top of the switch that has the green wire going to it and the throttle its self. if you have that its good you don't want to over adjust you want it to hit the switch ever so slightly to the point where it make enough contact that you get continuity this is important. so if that had been corrected then move to the throttle cable again and adjust the cable in a way that it was maybe 1/4inch of deflection but not pulling your adjusted idle switch open. next your want to have .63v on your tps and have it wing to 5.0v on link how ever there are ways to test with multi meter here is the link. http://www.vfaq.com/index-main.html this is a great website that I used to use a lot before I got link in my car. now you need to get your adjustment right otherwise you'll be in the same boast as before. with the 2g tps you will have the idle witch built into the tps and at that point your going to just need to adjust the tps as you would a 1g correct me if I'm wrong anyone . if you cant get it within spec you may have to much adjustment on your cable or your dummy idle switch pin bolt. Hope this helps, idle issue are the worse but as you tinker with these cars you'll know where to look and what to do next time.

I was also going to say if your ghetto logger will give you real time adjustments then adjust it to 0%. and if you cant get it there then you need to back out your dummy idle switch bolt or throttle cable a tad. let me know how it goes. but at 6.7 % that would cause your car to rum a little funny too.

In my experience the only time the idle actually surges or fluctuates was a result of a bad isc/iac or the ecu being fried because of the old tan iacs. Of course tps, biss, fiav, dirty TB, etc all affect idle, I've only had the actual up and down surging from the IAC. Just because it's black and the coils are in spec doesn't mean it's operating correctly. Pull it out, keep it plugged in and watch the pintle as you turn the key on and off. There's a few videos out there if you don't know how much it's supposed to move. When Im checking things like the iac, tps, maf, etc the easiest way is to just unplug them when the cars warmed up and make sure there is an obvious difference.
Of course you should still check the obvious, like the throttle cable (since it tightens as it warms up), tps calibration and fix your vacuum leaks, I'm just saying make sure your IAC is definitely working properly before you go chasing. If you did already and I missed it, apologies.

the cable was holding the plate just slightly open when warm, so i re adjusted it but im still only getting .8 ive done the iac test with it out, it moves in and out when you cycle the key not all to smoothly though. im thinking my ecu may be damaged? if im at idle and i turn on my ac or turn the wheel so the power steering puts a load on the engine and the car will die. the iac is supposed to adjust for that. ill try backing out the screw till i get 0% on my tps with my ghetto logger. if that doesnt change anything, im gonna take the ecu out and look at it. and my car is a 2g its a 1995 talon tsi awd

Yea the isc should adjust for added loads on the car like Ac and so on how ever if the iac hasn't been grounded well you fiddled with the biss it will make getting the setting correct s right nightmare. Does your ghetto logger allow you to check voltage iac position cause it it does aim for 30 and that by grounding the timing connector and adjusting the biss accordingly. Not sure of the colour of the 2g there is a blue a black and a brown so I've heard

yeah ive tried grounding it and got the idle to stay between like 650 and 1200 rpms but as soon as i turn the wheel all the way or turn on ac, boom car is off. it started raining like a mother but it just stopped so im gonna go try and pull the ecu and take a look at it. if it checks out, off to mitsubishi i go to see if they can fix it. also my ghetto logger doesnt show iac position

You can send the ECU to ecmtuning for testing and service. http://www.ecmtuning.com/product_info.php?cPath=24&products_id=33

91talonts1 said:

You can send the ECU to ecmtuning for testing and service. http://www.ecmtuning.com/product_info.php?cPath=24&products_id=33

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Sending it to ecm link is probably best if it is chippeded or epromed. But I'd even recommend a local electronics shop that has access to an esiolscope would be better then Mitsubishi there rob you blind.

so i adjusted my tps sensor so i can actually get to 0% took it for a cruise i would go wot and get 99.6% let of the gas and get 2% do it again and i get 4% then 2.7% and then sometimes itll come back to 0%. when my tps is at 0% my car idles between 500 and 700 jumping back and forth, any load on the engine at idle will make it stall. i didnt take the ecu out cause it started raining again, so i will do it tomorrow. My cars already been to 2 local shops and they have given it back cause they cant figure anything out either. so if the ecu checks out im gonna have to take the car to mitsu to fix it, or maybe even trade it in for one of the newer lancer ralliarts haha

well your car is bouncing around 500 - 700 either you have a vaccume leak or your stepper motor isn't functioning properly. have you adjusted the ics without grounding the timing pin?

91talonts1 said:

Locking the ISC doesn't necessarily put it right where the ECU wants it though. It puts it almost shut more or less taking it out of the equation. Another thing to note is the value ISCpos is not physically where the ISC is. It's the position the ECU has commanded, the ECU controls it like a fuel trim and just assumes the ISC motor is where it told it to be. Viewing ISCpos is also helpful in determining if you have a dead ISC or faulty ECU driver, which is all to common nowadays.

I'm not sure why you want to argue about the whole ISC thing here though. I told the OP adjusting the BISS without a logger may very well improve his idle. I just said doing it that way is not going to achieve the best results. And all you said is ground an idle connector, that doesn't exist so not very helpful. You made it sound like the timing ground pin was the same thing. Maybe you can tell the OP how to ground the diagnostic pin?
The way I use is what I've seen recommended by countless DSMwisemen and the guys who know more about the DSM ECU in the real world than anyone else.

Click to expand...

Since you clearly don't look through the actual idle stepper settings in link here's a picture of actual commanded idle step (granted this is an evo ecu since I don't have the dsm settings handy on my work computer). Fully warmed up 7-9 steps ISC position- just like where the ecu locks the ISC *according to you* when you ground lock the ISC. It's not taking it out of the equation, the sole purpose of locking the ISC and adjusting to target idle like I've said countless times already, is to center the ISC where it should be at idle. If that weren't the case the FSM aka Mitsubishi themselves, would want you to adjust the BISS BELOW target idle, because once the ISC opens it would bump the idle above whatever you set it at. This isn't a hard concept to grasp, I don't understand why you're struggling here.

The whole purpose behind locking the timing and the ISC position is because fluctuating ignition timing doesn't give a stable idle. Ever messed with the 1g adjustable CAS at idle? You can make the car idle at 500 rpms or 1200 rpms just by playing with the CAS, because ignition timing changes base idle. You ground the timing connector, and the ISC connector (diagnostic connector) to set it properly. It's pretty basic of a setup.

Edit: Had time to download link on the work computer, here's a tuned base log. 20 steps ISC position at 190F. Again, right around where the computer locks it.

i have tried messing witht the biss while the brown pin was grounded it doesnt help stablize idle, i have to have it back out most of the way to get it to idle where it does. im gonna replace my brake booster, maybe i have a vacuum leake there. i did a boost leak and it held pressure very well, i ran 20 psi through it and it seemed like all the air was coming out of my bov cause it cant hold that kind of pressure

have you checked to see if your throttle plate is open enough? you gotta look at the small stuff if you are having to back out your biss all the way then you are allowing more air past the butterfly that that isn't there already. so id start from scratch and loosen the throttle plate stopper and adjust the cable tension and everything from scratch. also put the biss screw in and back it out maybe 2 turns is what I am seeing as the normal

Tyeler18 said:

Since you clearly don't look through the actual idle stepper settings in link here's a picture of actual commanded idle step (granted this is an evo ecu since I don't have the dsm settings handy on my work computer). Fully warmed up 7-9 steps ISC position- just like where the ecu locks the ISC *according to you* when you ground lock the ISC. It's not taking it out of the equation, the sole purpose of locking the ISC and adjusting to target idle like I've said countless times already, is to center the ISC where it should be at idle. If that weren't the case the FSM aka Mitsubishi themselves, would want you to adjust the BISS BELOW target idle, because once the ISC opens it would bump the idle above whatever you set it at. This isn't a hard concept to grasp, I don't understand why you're struggling here.

The whole purpose behind locking the timing and the ISC position is because fluctuating ignition timing doesn't give a stable idle. Ever messed with the 1g adjustable CAS at idle? You can make the car idle at 500 rpms or 1200 rpms just by playing with the CAS, because ignition timing changes base idle. You ground the timing connector, and the ISC connector (diagnostic connector) to set it properly. It's pretty basic of a setup.

Edit: Had time to download link on the work computer, here's a tuned base log. 20 steps ISC position at 190F. Again, right around where the computer locks it.

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Again with this shit! I'm not even taking the time to read everything you posted. I am NOT the one who coined this whole shoot for 30 on the ISCpos thing, so again I don't know why you want to argue it with me for recommending that to the OP. I'm not continuing this back and forth with you, you aren't being helpful at all, just argumentative. If an ISC position of 10 is more desirable, why can I find a hundred posts like this one from Dave Mertz? I can find you the ones where they describe this method working better than the FSM process as well.

"An ISCPosition of 30 at normal warm idle is a good target regardless of mods. It represents a position of about 1/4 open on the ISC, giving room to close the ISC a bit if conditions warrant and provided the remaining 3/4 of opening to allow for fast idle and controlling the effective closing rate of the throttle.

Dave"

If you have a method that works better than what's recommended basically EVERYWHERE but the FSM. By all means outline it for the OP and actually contribute to the thread.

is going on here?

OP:

1) Check for vacuum leaks
2) Once leak free, read this: https://www.ecmtuning.com/wiki/idlesurge
3) If you can't find any issues outlined in the wiki, adjust your BISS per the factory procedure (because you don't have ECMlink). That procedure is outlined here: http://vfaq.com/mods/BISS-2G.html . Instead of hooking up a scanner, you can simply ground datalink connector pin 16, located here: https://www.ecmtuning.com/wiki/connectionproblem . Pay close attention to the idle stop portion, because if this sensor is not working properly, it will have a negative impact on you car's ability to know when to idle.

If you do all three steps above and the car still won't idle, I suspect you have more unresolved vacuum leaks, or underlying mechanical issues with the car.

91talonts1 said:

Again with this sh**! I'm not even taking the time to read everything you posted. I am NOT the one who coined this whole shoot for 30 on the ISCpos thing, so again I don't know why you want to argue it with me for recommending that to the OP. I'm not continuing this back and forth with you, you aren't being helpful at all, just argumentative. If an ISC position of 10 is more desirable, why can I find a hundred posts like this one from Dave Mertz? I can find you the ones where they describe this method working better than the FSM process as well.

"An ISCPosition of 30 at normal warm idle is a good target regardless of mods. It represents a position of about 1/4 open on the ISC, giving room to close the ISC a bit if conditions warrant and provided the remaining 3/4 of opening to allow for fast idle and controlling the effective closing rate of the throttle.

Dave"

If you have a method that works better than what's recommended basically EVERYWHERE but the FSM. By all means outline it for the OP and actually contribute to the thread.

Click to expand...

The fact that you failed to even read my full post just goes to show you have nothing to contribute or argue. I'm done arguing, I've made my point clear, offered plenty of advice and a method to correct his poor idle. If the method worked so well, I wouldn't be responding to 3 separate idle surge posts in the past 2 weeks regarding issues like this of people fiddle f***ing around with the BISS and ISC position. It's not rocket science, but again, I'm done arguing with bull headed people that don't have adequate knowledge/understanding of engine operation.

Tyeler18 said:

The fact that you failed to even read my full post just goes to show you have nothing to contribute or argue. I'm done arguing, I've made my point clear, offered plenty of advice and a method to correct his poor idle. If the method worked so well, I wouldn't be responding to 3 separate idle surge posts in the past 2 weeks regarding issues like this of people fiddle f***ing around with the BISS and ISC position. It's not rocket science, but again, I'm done arguing with bull headed people that don't have adequate knowledge/understanding of engine operation.

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That's funny. Just checked your post history and couldn't find but one post where you vaguely describe the fsm procedure for setting the BISS. And I don't see you arguing with anyone else about the ISC thing? This whole argument started when you disagreed with me that grounding the TIMING connector wouldn't help. You called it an idle connector, and made no mention of the diagnostic pin until I did. Show me the posts in this thread where you've given any kind of clear advice on how to follow the fsm procedure.
And yeah I suppose arguing that shooting for an ISCpos of 30 results in the BEST idle means I have no understanding of how an engine works...

Edit: And the fastidle tables you're referencing, are not a target ISCpos the ECU is trying to achieve.

Alright guys, calm damn. You both seem knowledgeable and have added good points to the conversation. I was unaware that grounding the plug on the firewall also steadied the isc.