ISC Assembly Thread - Rebuild your own ISC!!!

[DSMAddicted]

Gentlemen,
I am starting this thread with the intention to gather as much information and advanced technical info to be able to rebuild our own ISC motors, since this is a widely common problem among 1G owners and I am fed up with my Talon revving by herself at people when sitting at a stoplight.

I am sick and tired of my Idle Surge.
I am sick and tired of Mitsubishi's engineering errors.
It's not acceptable for a specific component to fail every couple of years like the 4G63 ISC for example. I bought a brand new ISC from Satan 18 months ago - brand new genuine ISC - which died after roughly a year. There's got to be a design flaw here, and I sure am NOT spending 200 bucks every year for my car to Idle correctly, so I wanna rebuild my own ISC.

Before narrowing down your Idle Surge problems to the ISC, please check out these links which will help you diagnose other common and cheaper to fix causes of erratic idle.

Link 1.
Link 2.
Link 3.

If the advices described in the above links still don't fix your issue, grab a voltmeter and test your ISC to find out if your ISC took a dump on you following this procedure.

Now, with that said you tested your ISC and... Surprise!!!
Values are all outside the acceptable ohm range. You now have two choices:
- Buy a new ISC from Satan - $200-$240 and watch it die again in a couple of years
- Buy a rebuilt ISC from CreboTech - $89 + Core and watch it die again in one year
- Grab a Phillips screwdriver and do some surgery on your own ISC, watch it die in one year and rebuild the sucker again when needed - $5-$20, all you'll need is questionable donor ISCs from your local Junkyard for coils

I went with option 3 and took apart the sucker. Save the o-ring or replace if needed. You'll wind up with two parts, which I will call the 'male' and the 'female'. Save the small spring on the bottom of the 'female'. I am not an electronics genius, so I am not 100% sure of this, common sense led me to the following statements:
- There are Two coils in the ISC
- They are located inside the 'female' (because I tested resistance again with the ISC apart and got the same exact values, so the coils are on the same assembly where the ISC plugs to the harness).
- They are interchangeable (installed opposite one from another - thanks CurtTSi)
- The bottom ones is the one that fails the most

This is where I got stuck.

I know that CurtTSi from this board successfully performed the above mentioned surgery on his Talon, I PM'ed him twice but he hasn't gotten back to me yet. I would love to get in touch with him to ask a few technical questions.
Here's one, perhaps some of you guys can answer it:

- What is the proper way of removing the internal coils without destroying the ISC housing?

Once I am holding the defective coil(s) in my hand, I will do backflips to find out who makes a compatible one and provide everybody with the info I found out. By posting this thread I want to give everybody the tools and knowledge needed to successfully rebuild our own ISCs when needed, since spending so much money every other year is not acceptable.

Let's all contribute to this post please, perhaps Moderators could make it a 'Sticky'.

Thanks everybody for the contribution.

Walter

 

[dsmturboawd]

im glad this thread is here. i too had a failed isc. i took it apart for fun after ohm testing it and once i got to the coils, i said forget it. it does look like a simple thing to repair however.

i ended up just buying a new one for 20 on the trader, and would love to be able to fix this busted one to sell for my money back/perhaps profit.

 

[AL92]

I thought many people just disconnect this thing after taking it out and pulling out plunger or heard you can just catch it at good idle.I disconnected mine today..what exactly happens with it disconnected.I thought their is fast idle thing in our cars and there is also and idle screw.Not sure about 2gs though.

 

[MrPikolo]

Originally posted by AL92
I thought many people just disconnect this thing after taking it out and pulling out plunger or heard you can just catch it at good idle.I disconnected mine today..what exactly happens with it disconnected.I thought their is fast idle thing in our cars and there is also and idle screw.Not sure about 2gs though.

Hmm, I myself have never heard of this. Can you go more indepth?

 

[DSMAddicted]

Originally posted by AL92
I thought many people just disconnect this thing after taking it out and pulling out plunger

That actually makes sense!
See, if you remove the ISC and take it apart, you'll notice that you can twist the 'male' side and watch the outer part increase or decrease in lenght just like a digital camera's Zoom. Now, if the outer part is extended completely and the ISC is reinstalled on the throttle body without being plugged to the harness, you'll wind up with an ISC frozen on the closed position.

Good point... has anybody tried this?

Regards,

Walter

 

[AL92]

I have read about this on other boards..don't have exact post right handy.I disconnected mine yesterday but didn't remove it just did it when it was warm and idling good.I haven't tried a cold restart but it worked fine hot so not sure what this stupid thing does.It appears to be redundant junk!! and not cheap to replace.!!

I would take it off move plunger out and disconnect and post back if it affects cold starts.There is the fast idle thing in their also and the idle speed screw so really whats the pont of the IDLE SURGE CAUSER as I like to call it.

 

[TalonTSi-AWD91]

Send an e-mail to [email protected] to buy a rebuilt ISC. I bought mine from him about 6 months ago, $54 shipped and hasn't had a problem yet.

 

[CraigB]

I new ISC should last for about 4 or 5 years. One of the main reasons that they fail is the seal between the FIAV and the throttle body will leak coolant on the ISC and short it out. Anytime you change a ISC you should change the seal.

You can also get a ISC from Hyundai for about half the cost of one from Mitsubishi. The Hyundai ISC is made by mitsu. It is just in a Hyundai box.

 

[DSMAddicted]

CraigB, great info, thanks.
If I blocked the FIAV then I should have no reason to worry about leaks (<--- no need to change gasket), right? If that is correct, after ordering a rebuilt ISC and swapping it, everybody should also block the FIAV and close the water lines through the TB, which would pretty much guarantee half-decade of regular idling? I can surely work with that.

If you don't mind me asking, how did you find out about those two valuable pieces of information?

Thanks!

Walter

 

[LaserCool]

Re: Repairing an ISC

I've done the surgery, about a year ago, and it was quite simple. I headed out to the local junkyard, and got an ISC out of a Hyundai Elantra, the ones that use a 4G63 block bored out to 1.8 L. The whole ISC unit would have been $20-30, but I simply opened the beast, clipped the connections between the coils and terminals, and took the coils for about $1-2.

I'd checked them in the field with my trusty Digital Multi Meter, and got acceptable ranged readings.

Apparently, the clerk didn't understand the fact that the coils were what I was really after. He charged me for "wires, assorted" , and I went home with them.

The trick then was to reassemble them into my original ISC, which took only a minor amount of soldering and extra wire lying around the toolbox. The only problem was making sure I oriented the coils proplery. Since each coil section is actually two coils, and there are two sections, then you have four different coils here allowing a range of positions for the pintile with respect to the hole.

No twisting was needed on the pintle. I just left it in it's factory position, but swapped out the coils. And voila, I had a working ISC. It continues to work fine.

 

[CraigB]

DSMaddicted

I work for a Dodge and Hyundai dealer as a tech. I have worked on these cars for many years. I have also had 5 DSMs.

CraigB

 

[DSMAddicted]

Originally posted by LaserCool
but I simply opened the beast, clipped the connections between the coils and terminals, and took the coils for about $1-2.

I'd checked them in the field with my trusty Digital Multi Meter, and got acceptable ranged readings.

LaserCool, you just posted what I was looking for.
Could you kindly be a bit more specific especially on the first sentence I quoted? Pardon the ignorance, but what do you mean by 'clipped the connection between coils and terminals'?
Also, how did you check the coils once they were out?

Originally posted by CraigB
I work for a Dodge and Hyundai dealer as a tech. I have worked on these cars for many years. I have also had 5 DSMs.

Well, that definitively justifies your knowledge. Thanks Craig.

Guys, thanks to your patience and experience and to my good intentions I should soon be able to write a sweet and detailed VFAQ for everybody to benefit from.

Regards,

Walter

 

[LaserCool]

Originally posted by DSMAddicted
LaserCool, you just posted what I was looking for.
Could you kindly be a bit more specific especially on the first sentence I quoted? Pardon the ignorance, but what do you mean by 'clipped the connection between coils and terminals'?
Also, how did you check the coils once they were out?

Sorry for the late reply. Too much work, and too much preparation from the GRE.

At any rate, the device is rather simple. It's a "stepper motor"- in other words, a plunger which can be moved in and out to 5 different depths. The ECU uses different sensors to determine what position the ISC should hold depending upon the demands placed on the engine.

For example, if you have A/C such as I do, you'd notice the car rev's up when you turn it on, and rev's down when you turn it off. Same thing's true for other events, such as decelerating or operating high-draw electrical appliances.

At any rate, the ISC has two coil-like structures encased in plastic that encircle a cylindrical shaft. This shaft is the plunger of a solenoid formed by the ISC, and the coils draw the shaft by magnetic fields. The plunger is drawn in, and the pintle end of the ISC is removed from it's hole in the throttle body allowing more air to pass into the engine, etc.

The coils themselves are the subject of our conversation. Each coil pack actually contains two coils within it, and there are two coil packs of two coils each. This makes for 5 positions as you energize each of the 4 coils- none energized is the fully closed position, 4 energized is the fully open position with respect to the hole in the throttle body.

Incidentally, when the #10 pin on the ECU interface (next to the interior fuse box) of 1st gen 4g63's is grounded for setting the base idle on the BISS, this tells the ECU to energize only two coils, giving the "middle" position, and allowing the engine maximum range to increase or decrease the idle.

So, on to the coils: each coil-pack has three terminals, which extend by wires to the plug on the outside of the ISC. This plug leads to a connector that feeds back tot he ECU.

Now the center terminal of the coil-pack is the common terminal, which both coils share. When checking the resistance of the "new" coil pack, check across each of the outer terminals and the center one to determine the right resistance. I don't have the proper values handy, but a good Haynes' or Chilton's manual should be part of your toolkit.

Now that you've checked all the resistances and found them to be good, carefully note the postion of each coil and how it feeds to the plug. In the field, I just clipped those connections, knowing I could re-solder them with new wire back home. I used leftover telephone wires (thin, like 25 ga), and just made sure I soldered carefully.

When in the field, note carefully which terminals from the plug feed the "front" coil and which feed the "rear" coil along the shaft. I doubt it would make much difference, but just in case it did, I drew myself a little sketch on some paper scrap I brought with me.

After about 15 min of soldering, I was ready to try it. Popped it in, fired it up, re-set the BISS and I've had no problems since.

P.S. If you do use my information to do a VFAQ, I ask that I be fully credited for the information.

 

[jjsacidy]

is wrong with these things? i have yet to find a fully functional one, cept for a new one. hmmm mine has 12, 45 at 30 ohms and 23, 56 either open or at 50 ohms. 56 goes from open to 50-70 ohms how ever it feels.......... but then atleast my isc seems to work.

-----does the fiav control the isc or is a seperate air path?!

 

[myblack98gst]

A fairly common fix to this I have seen is to removed the bottom half of the throttle body and make a plate to seal it off. then cut down the screws and reinstall. and set the idle where you want it the ISC can't come to life and mess with it when it feels spunky!

 

[myblack98gst]

Just a update I made this "plate" for my car today and it works AWESOME.

before:
on a cold start it would idle at 500 or so rpms or just die!
when warmed up it would vary between 600 and 1,600 rpm idle!
would die everytime I turned the a/c on at idle (had to shut it off at lights)
would die if I let it idle down from a rev or coming out of gear (unless you blip the throttle right around 1,500 rpms)

Now:
idle is 850-900 on cold start
950 when warm
drops to 750-800 with a/c on
didn't die one time all day


I did not take any pics of it while making it but if anyone is interested to see I will spend 5 minutes making another one and take a pic or ten!

 

[heavyD]

I don't know if anyone knows or not but the original 2G ISC's have now been superceeded by a newer model ISC. The body is black and looks different than the last two OEM ones I have had. This new one seems to be working excellent. I will cross my fingers.

 

[Tallen]

I use that one too. If I remember correctly, its 40 or 50 ohms across coils.