If you got it blocked off idle will be hard to stay running until its starting to warm up. If you bypass it like I did it deletes the fiav portion and you can stop running coolant to the throttle body. Of course you'll need a good biss properly adjusted along with a good isc adjusted correctly through ecm link if you have it. Make sure your tps sensor is working properly too.

The ISC cannot be adjusted itself. The only things that can be adjusted is the IPS which shouldnt of been touched from factory, the TPS, the BISS, the throttle cable and the CAS

The problem is previous owners who dont know there is a BISS since it is under a cover and adjust the IPS as the BISS which will throw things all out of wack. Also if your throttle cable is too tight without any slack then you will have a higher idle than normal when warmed up since it is pulling the throttle plate open slightly.

Another thing that can cause a high isle is the engine coolant temperature sensor. If it isnt reading right then the ECU can think the engine isnt up to temperature and keeping the ISC open which also increases the idle.

The CAS being out of adjustment can cause high idle too. In my case everything was out of adjustment, the TPS, the IPS, the CAS which was about 12degree atdc and now that I have all those set correctly I cant get the idle under 1200 until the BISS bottoms out and stalls, no codes or anything so I am currently putting new seals in the throttle body and then going from there.

You could also just have a bad ISC where it is stuck open. There are so many things that you have to check and go through for an idle issue that you can drive yourself crazy. All of these things being out of adjustment, vacuum leaks somewhere, throttle body seals leaking, FIAV housing leaking, PCV issue, throttle cable not having slack and from other wisemen on here the throttle cable gets tighter as it warms up, leaky gaskets, EGR leak.

I have been dealing with my idle issue for a while know, at least a few months and like I said earlier I am to the point where I have to do the throttle body seals and getting yet another entirely new BISS kit. I kind of messed up the head of my BISS though it still works and the o-ring is maybe a month old with no actual drive time I dont like that it doesnt have its cap and the head is getting stripped from all the testing.

95_gsx_2g said:

If you got it blocked off idle will be hard to stay running until its starting to warm up. If you bypass it like I did it deletes the fiav portion and you can stop running coolant to the throttle body. Of course you'll need a good biss properly adjusted along with a good isc adjusted correctly through ecm link if you have it. Make sure your tps sensor is working properly too.

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I understand with it blocked off that it would be hard to stay running at first.. but right off the bat on a cold start it revs high up to 1400rpms.. another dsmer told me it's called idle surge.. and gave me a list of the things that could throw it off.

Cherry said:

The ISC cannot be adjusted itself. The only things that can be adjusted is the IPS which shouldnt of been touched from factory, the TPS, the BISS, the throttle cable and the CAS

The problem is previous owners who dont know there is a BISS since it is under a cover and adjust the IPS as the BISS which will throw things all out of wack. Also if your throttle cable is too tight without any slack then you will have a higher idle than normal when warmed up since it is pulling the throttle plate open slightly.

Another thing that can cause a high isle is the engine coolant temperature sensor. If it isnt reading right then the ECU can think the engine isnt up to temperature and keeping the ISC open which also increases the idle.

The CAS being out of adjustment can cause high idle too. In my case everything was out of adjustment, the TPS, the IPS, the CAS which was about 12degree atdc and now that I have all those set correctly I cant get the idle under 1200 until the BISS bottoms out and stalls, no codes or anything so I am currently putting new seals in the throttle body and then going from there.

You could also just have a bad ISC where it is stuck open. There are so many things that you have to check and go through for an idle issue that you can drive yourself crazy. All of these things being out of adjustment, vacuum leaks somewhere, throttle body seals leaking, FIAV housing leaking, PCV issue, throttle cable not having slack and from other wisemen on here the throttle cable gets tighter as it warms up, leaky gaskets, EGR leak.

I have been dealing with my idle issue for a while know, at least a few months and like I said earlier I am to the point where I have to do the throttle body seals and getting yet another entirely new BISS kit. I kind of messed up the head of my BISS though it still works and the o-ring is maybe a month old with no actual drive time I dont like that it doesnt have its cap and the head is getting stripped from all the testing.

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I read in the hanes manual that yoy can check the continuity on the FIAV and they should all come up the same number.. well mine didnt so i replaced the FIAV and o_ring gasket.. i replaced the throttle body gaskets, both of them. I also replaced the gasket in between the top and bottom of the thorttle bodie.. which went bad and leaked coolant thats why i even started messing with the TB... I took everything off and cleaned it really well and i forgot to mark where the TPS was adjusted at. Also i throttle plate is closed. There is a way to connect aligator clips from the plug pins to the actual TPS and with a volt meter the number that comes up will either tell you to move it forward or back.

Its funny because the car ran fine with all crap in the TB.. and now its all clean and runs like shit.

Cherry said:

The ISC cannot be adjusted itself. The only things that can be adjusted is the IPS which shouldnt of been touched from factory, the TPS, the BISS, the throttle cable and the CAS

The problem is previous owners who dont know there is a BISS since it is under a cover and adjust the IPS as the BISS which will throw things all out of wack. Also if your throttle cable is too tight without any slack then you will have a higher idle than normal when warmed up since it is pulling the throttle plate open slightly.

Another thing that can cause a high isle is the engine coolant temperature sensor. If it isnt reading right then the ECU can think the engine isnt up to temperature and keeping the ISC open which also increases the idle.

The CAS being out of adjustment can cause high idle too. In my case everything was out of adjustment, the TPS, the IPS, the CAS which was about 12degree atdc and now that I have all those set correctly I cant get the idle under 1200 until the BISS bottoms out and stalls, no codes or anything so I am currently putting new seals in the throttle body and then going from there.

You could also just have a bad ISC where it is stuck open. There are so many things that you have to check and go through for an idle issue that you can drive yourself crazy. All of these things being out of adjustment, vacuum leaks somewhere, throttle body seals leaking, FIAV housing leaking, PCV issue, throttle cable not having slack and from other wisemen on here the throttle cable gets tighter as it warms up, leaky gaskets, EGR leak.

I have been dealing with my idle issue for a while know, at least a few months and like I said earlier I am to the point where I have to do the throttle body seals and getting yet another entirely new BISS kit. I kind of messed up the head of my BISS though it still works and the o-ring is maybe a month old with no actual drive time I dont like that it doesnt have its cap and the head is getting stripped from all the testing.

Click to expand...

The old biss screw for some reason the last owner had it jammed all the way down which blew out the oring. So i replaced that to and put it so it wasnt stuck like the last one. Also i did put the TB gaskets on backwords at first and you heard a loud hissing due to it sucking in air. Well i figured out the correct way and now no more loud hissing.

The TPS should be set to .5v at closed throttle and that's it. You check it between pins 2 and 4. Pin 1 is voltage in, 2 is voltage out and 4 is ground.

It also seems like you got the FIAV and ISC a little mixed up. The FIAV is basically a thermostat but instead of water it's air. Water flows around it through the housing and once the housing heats up it closes. This is for cold starts and works together with the ISC which is the motor in the FIAV housing. It does a few things. Idle surge doesn't just happen at start up and happens when it is idling, sometimes it can happen fast or slow and it will let's say your car is idling at 1100 it will go between that and 1500 steadily and it is completely annoying.

Your throttle plate shouldn't be completely closed and you should be able to see a little sliver of light around it. If it is too much then someone might of messed with the IPS which tells the computer the throttle is closed. This is the absolute last thing you should touch. I can't tell you how many times my dad asked if that is how you adjust the idle so if it went to a mechanic for this issue that didn't know better, or the previous owner touched it then it can cause a high idle.

If your CAS is out of adjustment and your timing isn't right it will throw everything out of wack as well. Set the TSP to .5v, let the car warm up, then check the timing which I have read it should be 5 degrees BTDC and then adjust the BISS with the timing plug and diagnostic plug pin 10 grounded. Set the idle to 750rpm +- 50 rpm. Then after all of that is done do a boost leak test. I never done that on my non turbo because the non turbo seals would probably just blow out so I just rebuilt the throttle body and I'll see how it goes today.

If you can't get the idle set at 750rpm though it's likely there is an air leak that's why I decided to do a rebuild which is actually really easy.

What is the CAS? Did you read any of my post? Lol. MY CAR IDLED FINE BEFORE I MESSED WITH THE THROTTLE BODIE!! so its something to do with that.. the FAST IDLE AIR CONTROL was bad so i replaced it and the o ring. . Also the gasket thats inbetween the bottom and the top of the Throttle Bodie went bad leaking coolant into where the THROTTLE PLATE IS cause it stick open.. i fixed it and got it to snap back like stock and put a new gasket.. also while i had it off and cleaning the THROTTLE BODIE i took the THOTTLE POSITION SENSOR off and didnt mark where its suppose to be because i forgot. Now im dealing with trying to get my normal.idle back

Cherry said:

The TPS should be set to .5v at closed throttle and that's it. You check it between pins 2 and 4. Pin 1 is voltage in, 2 is voltage out and 4 is ground.

It also seems like you got the FIAV and ISC a little mixed up. The FIAV is basically a thermostat but instead of water it's air. Water flows around it through the housing and once the housing heats up it closes. This is for cold starts and works together with the ISC which is the motor in the FIAV housing. It does a few things. Idle surge doesn't just happen at start up and happens when it is idling, sometimes it can happen fast or slow and it will let's say your car is idling at 1100 it will go between that and 1500 steadily and it is completely annoying.

Your throttle plate shouldn't be completely closed and you should be able to see a little sliver of light around it. If it is too much then someone might of messed with the IPS which tells the computer the throttle is closed. This is the absolute last thing you should touch. I can't tell you how many times my dad asked if that is how you adjust the idle so if it went to a mechanic for this issue that didn't know better, or the previous owner touched it then it can cause a high idle.

If your CAS is out of adjustment and your timing isn't right it will throw everything out of wack as well. Set the TSP to .5v, let the car warm up, then check the timing which I have read it should be 5 degrees BTDC and then adjust the BISS with the timing plug and diagnostic plug pin 10 grounded. Set the idle to 750rpm +- 50 rpm. Then after all of that is done do a boost leak test. I never done that on my non turbo because the non turbo seals would probably just blow out so I just rebuilt the throttle body and I'll see how it goes today.

If you can't get the idle set at 750rpm though it's likely there is an air leak that's why I decided to do a rebuild which is actually really easy.

Click to expand...

You can also check the FAST IDLE AIR buy checking continuity between the six pins on it.

Nevermind. CAM ANGLE SENSOR... AGAIN MY CAR RAN FINE BEFORE I MESSED WITH THE THROTTLE BODIE.. I DIDNT TOUCH THE CAS.

Yes I did read your post and just because you have been messing with the throttle body doesnt mean something else has went out or is out of adjustment. There was a block off plate there for a reason and being a street car (I am assuming) there was an idle issue before the plate was installed most likely

And you replaced the ISC, not the FIAV from your description. The ISC is the idle speed control, the FIAV is the fast idle air valve and it is located towards the front of the car in the FIAV housing. There are 2 passages in the FIAV housing, one that goes to the FIAV and one that goes to the ISC. Once the car warms up the FIAV closes completely.

So many things can a high idle.
-TPS out of adjustment
-CAS out of adjustment (timing)
-ECT(ECU) not reading properly
-Thermostat, if it opens too early the engine doesnt get to operating temperature and the ISC will still think it is a cold engine and let in more air to try to get it to operating temperatures.
-EGR leak
-Vacuum leak
-Throttle body seal leaks
-BISS out of adjustment
-IPS out of adjustment

Those are just from what I have found on this site that I can remember. It doesnt take long to check some of these and it is good to check them so you can go off the checklist to find where the issue is.

The TPS is very easy to set though. You have pin 1 which is voltage in, pin 2 is voltage out to the ECU, pin 3 is empty (for a 1g) and pin 4 is the ground. Hook up a digital multimeter to pins 2 and 4 with the key on and set it to .5v at closed throttle. Once it is set, open the throttle plate all the way and it should read 5v or very close to it.

Another warning, you shouldnt touch the IPS (idle position switch) which tells the ECU the throttle plate is closed since it also acts as the stop screw. If you do have to adjust it then it is 15/16 of a turn after it makes electrical connection. A lot of people actually think this is where you adjust the idle because the BISS is kind of hidden. My dad has asked me several times if that was where you adjust the idle even after me telling him no and showing him where the BISS is located.

Regardless, it takes a few minutes at most to check some of these things like the timing. If you want it to set up properly then you should at least check to see if its set right. If it is, great you dont have to mess with it, if it isnt then you can adjust it.

I replaced the FAST IDLE AIR .. Its at the bottom where the coolant line are.. and i replaced the o ring... i just looked at the reciept and it says Fast idle air control. The TPS Is at the the top and thats what you adjust as it would tell how much the throttle plate is open. .. i know i didnt replace the IDLE SPEED CONTROL cause thats $199.99.. i really thing that that is just out of adjustment.. i dont drive the car everyday.. i just start it every other week.

I been meaning to try and test the TPS. I just got aligator clips n wire so i have test leads.. because with it plugged in i cant put a multi meter on the pins .. ill check back n let you know.. thanks

How are you suppose to check it? The one side is a plug and the other is pins.. i get what to do on the pin side but what about the plug side? I dont wanna cut wires..

Also i put the block off plate back in ... without it my idle was at 2700rpm. And with it brought it down to 1500rpms ish.. so im gonna keep it in as its always been in and ran fine.. especialy after it was built. The guy at dmv years ago said he could believe how good it ran. And its cammed..

Ok so i just to the car.. I checked to make sure there's power getting to the plug. I'm getting just about 5 volts. Then I I hooked up my ghetto test plugs and off the TPS I'm getting 4.56 volts with just the key on and the engine not running. So if that needs to be .5 then i need to adjust. I will get back to you in a few..

There should be 5v going in on pin 1. You should have .5v on pin 2 with the key on and closed throttle. You can with your digital multi meter is slide the probes next to the wires, they will make contact as long as you dont force them too far in and damage the plug.

The ISC is also known as the IAC or Idle air control. Looking it up in the manuals however it is called the ISC or idle speed control which it is controlled by the computer to let more air in or less air during many things like start up (along with the FIAV) letting off the throttle, when the fans come on, when the ac pump is on and some other stuff as well. The FIAV or Fast Idle Air Valve is just open at start up until the car gets to operating temperature and then closes sealing off the air passage.

When people talk about the FIAV even in the service manuals, it is talking about what is listed above and not the motor. These automotive parts chains have things labeled wrong at times or dont even show it for the car even though the part does exist. Like the FIAV housing for example, it isnt listed for a Mitsubishi eclipse or any of the others that are just like it, it is however listed under the Mitsubishi 300gt VR4. Same exact part, same numbers as the original, but it just isnt listed for the Eclipse.

So you have a new ISC motor and o-ring, just need to make sure everything else is adjusted to where it should be and then try setting the idle as it says to do in the vfaq and if you need a link I can find it for you. If you cant get it to idle at 800-700rpm then you will have to do a boost leak test which is what I am going to have to do. If there are leaks then you have to find and fix them, if not then some other things might be wrong.

If it comes out that you dont have a leak then it could be in the engine coolant temperature sensor that goes to the ECU. This can go out or send a wrong reading telling your ECU that your engine isnt up to operating temperature yet and the idle motor lets more air in. It could be that your thermostat is for a lower temperature as well which will keep the coolant at a lower temperature and the engine never gets to operating temperature which will tell the ECU to increase the idle until it gets there, it never will and you get a surge.

It could also be the Idle Position Switch which is also the stop screw for the throttle plate. If you arent the original owner they might of adjusted this switch instead of the BISS or even a mechanic that doesnt know where the BISS screw is. If that is the case the FSM says to turn it 15/16 of a turn more after it makes electrical contact. Some people just make the air gap as small as possible though without the throttle plate hitting the throttle body walls so it wont get stuck, usually looking through the throttle body at a light source where the gap around the throttle plate should be around the width of a piece of paper. I wish that I could find a feeler gauge measurement but I havent been able to find one yet. It would be much easier to set if it was based off of a feeler gauge than a rotation of a screw.

It can be a nightmare and some people fight idle issues for months even a year.