Good or Bad ISC

[Dr DSM]

is my ISC making normal motions?
good or bad ISC? - YouTube

I dont know if it needs replaced or not.

 

[92AWDHX40]

DSM ISC motor testing & Replacement - YouTube

http://www.dsmtuners.com/forums/newbie-forum/184093-how-test-isc-motor.html

 

[Dr DSM]

all coils are good, but is the movement normal?

 

[AlexSza]

I can't view the video but it should vibrate very little in and out as you turn the key on and off, not starting.

 

[Dr DSM]

ok, thats what it looks like its doing

 

[AlexSza]

Double check the coils, I recently had an isc go out and it dragged my ecu with it, unfortunatley

 

[Dr DSM]

ok, I think the ECU is bad also but i just wanted to make sure the ISC was good.

 

[minimoose]

Make sure when your testing the isc like you were in the video press with a finger on the end slightly, not alot, and feel for weak spots in the motion.

 

[DSM1G90]

Plunger goes in and out to set idle speed according to temp readings. But, beforehand, you need to reset the ISC before doing the BISS screw adjustments.

 

[Dr DSM]

What do you mean weak spots?

 

[minimoose]

Hold the isc in your hand and while your friend turns to acc and off press slighty on the probe end and press gently against it if it slips while your holding it it could have a bad spot internaly. Dont hold onto it like its a contest against man vs machine but give it a little resistance.

 

[DSM1G90]

it could have a bad spot internaly

Measuring resistance across the four coils are an easier way if dead spots are in question.

That way, it can be taken out just once, for a few DSM owners DON't know that the 1990 version of the ISC was mounted in a horrible place where we have to take the throttle body apart to get to it, let alone to take it out just to "poke the end". 1991's and on, Mitsu got smart to place it where it can be taken out much easier.

 

[kchaazz]

Just remember that if your ISC coils check out ok and you are still having issues, the next step is to check out the ISC driver chip on the ECU. Just putting this info out there for those who might run into this situation

 

[minimoose]

Just remember that if your ISC coils check out ok and you are still having issues, the next step is to check out the ISC driver chip on the ECU. Just putting this info out there for those who might run into this situation

Nice. Which is the isc chip? I know the knock is the large flat one.

NM its the couple of black smaller things in the right hand.

 

[Boomdeeze]

I had an ISC which all coils were in spec and the end moved like it should but had a slight rattle to it when it moved. Car ran like crap so threw a old one on there and it fixed the problem. Something very minimal was wrong with it so the ecu wouldn't regulate the idle but would still pass the tests.

 

[minimoose]

I think im having the same problem cause my car runs like crap too. Mine makes noise that you can hear easily when turning the key on and off.

My coils are in spec hot and cold but car runs horriable and I keep geting a maf code even with a known to be good maf. And I apologize for hijacking...

 

[DSM1G90]

What could knock out the driver is a direct short to ground by the plug itself since there is voltage coming from the ECU that goes through the sensor, then goes back into the ECU..and it doesn't take much current to take out a driver..

...why it's a good idea to disconnect the negative cable from the battery before disconnecting any sensor connections.

I keep geting a maf code even with a known to be good maf

Have you also did the resistance test in the MAF connector, and if readings are good, it could be the driver on the ECU board has gone out. OR, a simple ground trace has blown open to that driver causing MAF code errors.

Why I stress above to disconnect the battery before messing with sensors... for I've been there and done that, but worse: I had all sensors coming out with error codes. Thus, I cracked open the ECU and found that I toasted out the entire ground traces in my ECU where I sent it off to Motoguys for a rebuilt one. I had touched two plugs to ground and "poof!" goodbye traces.

 

[minimoose]

Crap zone sells a 90 iac valve new for 240$ ... 90s are horriable for parts.

Is is possible to use the 1GB isc valve if you make a jumper harness to make up the length issue?

I havent checked it yet. What are the specs for testing it? Whats good and whats bad number wise?

 

[DSM1G90]

http://dmtalon.v8eaters.com/ISC.html Check this link out to test IAC units.

1990-1997 Mitsubishi Eclipse Idle Air Control Valve - Air Intake - Standard Motor Products 90-97 Eclipse Idle Air Control Valve - 7082-07034675 - PartsGeek Why you just NEVER get parts from "CRAPZone" - oil, plugs, cleaner, et.al. - shelf stuff is okey with comparible pricing...but....you know the rest of the story.

Good luck-DSM

 

[92AWDHX40]

You also should test the isc to make sure that they are in specs. two different ohm readings for the black, and tan ones.

 

[LV-DSM]

1ga and 1gb TB will fit the same ISC if you extend the wires. After months of troubleshooting I ended up switching to a 1GB TB. The ISC is in a terrible location on the 90. While troubleshooting I picked up a $90 black ISC from National Auto. Look for a coupon if you want to go that route. If you do however, check for proper resistance right out of the box. My first one had good resistance, but when I turned it upside down to test a second time, I found different readings. I recommend this for testing any ISC. I suppose it's hit or miss. Damn you ISC! Good luck with this. Almost caused me to sell the car.

Anyone know if there is an obvious way to tell if the driver chip is blown? I imagine there will be a burnt spot on the chip, but not sure. Just curious.

 

[92AWDHX40]

http://www.dsmtuners.com/forums/tuning-engine-management/342860-ecu-damage.html



I would post a picture of the board or have it looked at just to make sure, a bad isc can damage the ecu.

 

[Dr DSM]

http://www.dsmtuners.com/forums/tuning-engine-management/342860-ecu-damage.html



I would post a picture of the board or have it looked at just to make sure, a bad isc can damage the ecu.

ecu is out! - YouTube

(.. that ain't nice ...)

Plunger goes in and out to set idle speed according to temp readings. But, beforehand, you need to reset the ISC before doing the BISS screw adjustments.

how do you reset the isc?

 

[kchaazz]

I think im having the same problem cause my car runs like crap too. Mine makes noise that you can hear easily when turning the key on and off.

My coils are in spec hot and cold but car runs horriable and I keep geting a maf code even with a known to be good maf. And I apologize for hijacking...

If your car is running like crap and you keep getting the maf code, you need to check for vaccum leaks at the TB and between intake manifold and head. A large enough leak will allow enough air to bypass the maf and the ecu will throw the code. Is the CEL on at idle? Does it go off when you rev the car a bit??

 

[minimoose]

It comes on instantly when you start the car. I have all new gaskets and im running 25 to 20 lbs of vac while at an idle.