Horrible Idle Problem

DSMKevan · Apr 11, 2004

Hi, Ive got a 1990 tsi,with 130,000 miles, with a major idle problem. After warming up (about 5-10 minutes of driving) it dies at every stop we make. And it gets worse and worse as you drive more and more. Seems like some weird heat related idle problem.

Whenever we get at a stop, it bogs down to a REALLY low idle then stalls right away. It stalls when you put the clutch in at a stop, so we are left foot braking it and putting it in neutral. That seems to work fine. I can notice that it smells quite rich whenever it stalls, or "bogs". And if the engine does not die, it idles very low, and smells rich too.

Other than that the engine runs like a dream. And we (myself and my uncle, who is a very good mechanic) have only been able to conclude that it is the IAC (idle air controller) motor (aka ISC idle speed controller).

What are some other possibilities of our plight? I havent gone through with the manuals troubleshooting procedures yet. I hope there is an alternative to buying a new IAC.

Thanks

CurtTSI · Apr 11, 2004

My car did the same thing and it was the ISC servo. After the car has warmed up, check the coil resistances on the ISC. Mine tested good when cold, but one coil tested open circut when hot. The ISC that I am now using is one that I rebuilt from parts from 2 bad units.

DSMKevan · Apr 11, 2004

I knew it! Stupid thing is probably burned out from sitting too long. Is it ok to use a used one?

And how do you remove it from the car? Is it easier to take off the throttle body first, or just unbolt the ISC?

One more question:
Could I just unplug the ISC, then just adjust the idle normally, and it would idle at that set speed all the time?

racer · Apr 12, 2004

No ,u can not do that.U need to replace it.I sugest u to buy new one.
Do not play with it.It will cost u like 50$ extra for new one but what if u like ur car who cares.
U do not have to take out ur trotle body.Just unbolt the ISC from it.It is conected with 2 long ass bolts and that is.If ISC doesnt help then check the Ignition sistem. :thumb:

DSMKevan · Apr 12, 2004

How would I hurt it if I just unplugged it? And I think its much more than $50 for a new one.

CurtTSI · Apr 12, 2004

It would be OK to install a used ISC, providing it is any good. There are a lot of bad ones out there. I bought 3 of them from a guy, who said they were all good. Turns out all 3 were bad. However, it worked out OK, since I was able to salvage enough good components from the 3 to make one good one. Since I only paid $30 for the three, it was still a good deal.

Another problem that you have is that the ISC on the 90 models is different than the ones on all the later models. This makes finding a good used one more difficult.

DSMKevan · Apr 12, 2004

Great...I hope my uncle will be able to find one. If not its one $300 trip to the mitsu dealer :cry:

CurtTSI · Apr 12, 2004

Before buying another ISC, test the one you have to make sure that it is bad. Don't spend big $$$ unless you know that the ISC is actually the problem.

DSMKevan · Apr 12, 2004

Of course, how do you test the ISC? Do you just use a multimeter or voltmeter?

CurtTSI · Apr 12, 2004

A digital volt/ohm meter works best. You can get one cheap at Radio Shack. Unplug the 6 pin ISC connector. Measure the resistances between pin 2 & 1, 2 & 3, 5 & 4 and 5 & 6. All four readings should be between 28 and 32 ohms. If one of the readings is a very large number, you can be assured that the ISC if bad. Since you only have the problem when hot, make the measurments after the car is warmed up and and the problem exists.

markGSX · Apr 12, 2004

Just curious, what is your vacuum reading at idle?

white1997gs · Apr 12, 2004

color me retarded, but what the hell is an ISC?????????

I know, i know, I'm the resident FNG

white1997gs · Apr 12, 2004

oh wait, nevermind, I saw it in the first post.........please don't pelt me with stones

racer · Apr 12, 2004

well i bought mine brand new for 160 from mittsubishi .I duno about 90 model.

DSMKevan · Apr 12, 2004

160?! The non-90 ones are 280 on machv.com!!! And the 90 are $280 too....

I dont have a vaccum or any gauges setup yet. Once my uncle makes a trip to autometer headquarters we can get all the free gauges we want

. Im thinking a boost, vaccum, and a EGT. Maybe a 02 volt one too.

I dont have the car as of now, but Ill have my uncle test them.

DSMKevan · May 10, 2004

Goddamnit!!! I just got back from chicago, tested the ISC.....all connections were at 0 ohms...I think that means its dead. The idle problem has gone away (probably cuz the ISC is dead), but now it idles fine at 1400 rpm. I think I will either have my uncle order an ISC he found for $300.....WTF?!?! what am I thinking?!

I might just unplug the ISC or block it off, and if it gets any worse Ill just get a good condition used one, or a crebotech one.

Could I leave it unplugged? :confused:

SpeedFreak03 · May 10, 2004

Heres how to properly test it: http://dmtalon.v8eaters.com/ISC.html go to a junkyard with a 6-volt battery and a multimeter and start testing. All ISCs are the same for 2.0L engines, N/A or turbo. If you cant find a good one, here's a new one for $216 from Conicelli Mitsubishi: http://www.trademotion.com/partloca...1&make=24&model=Eclipse&year=1990&catalogid=1
Make sure you get the 2.0L one.

DSMKevan · May 10, 2004

Ok, I tested the resistance between pins 1-2 2-3 3-4 4-5 5-6 and they all measured 0 ohms. I havent tried the 6volt test, but Ill tell my uncle to do it. I dont have the car with me, its in chicago with my uncle.

Once the ISC was unplugged it seemed to idle consistent enough, just it idled at 1400 rpm. I think that it would be fine if we just unplugged it and adjusted with the BISS properly, but I could be wrong...so:

Can I unplug the ISC, or block off where it was on the Throttle Body, and still just run like normal?

TalonTSIYHL · May 14, 2004

when testing the ISC with the 6 volt battery, i wasnt sure if i had bad connections or the ISC was bad. Can i do the battery test with the ISC off of the TB???
(i got good results from the multimeter test)

symptoms: really rough idle on a cold start, RPMs vary from 800 to ~500 and sound like it wants to stall, decrease in low end power(during vac), boost is good, with the throttle barely open it hesitates untill more pressure on the accelorator is given

Thanks for the replies.

TalonTSIYHL · May 14, 2004

More symptoms:
it sounds like the engine is sputtering when in vac, very little power and major hesitation. when the brake is applied and car comes to a stop, RPMs go real low and feels like a stall is going to happen.
When i warmed it up and tested the ISC all showed a value of 38 ohms
it idles at 1k when the ISC isnt hooked up.

another problem: when i start the engine a cloud of white smoke comes out of the engine, cant see from where but it stops after a couple of seconds.

(92 auto TSI w/120,000)
What could be the causes of these problems??? PLEASE HELP!

TalonTSIYHL · May 16, 2004

ANYONE???
could a clogged cat cause all these problems?

td06hkiko · May 16, 2004

HOw do you know if your Wastegate Actuator is going bad? I have an 20g td06h internal 34mm flapper door. Do you remove the pin and see if the Flapper is moving freely?? I've already checked for boostleaks. I also found that my Vacuum hose from the wastegate actuator was cracked. So I replaced that and I am still getting some stuttering above 15psi. Someone please Reply. Thanks.

AWDPSI · May 19, 2004

i have a good 90 isc motor for sale. I bought it for a 90 that my brother was getting but then the basturd got a 91 instead. If someone wants it, its good and ill take 45 shipped. That is a good deal because they are hard to find especially good.

Scott
[email protected]

TalonTSIYHL · May 19, 2004

i heard from someone that 90s are different from other years, is this true?

DSMKevan · May 19, 2004

Yes and quit stealing my thread ahha jk :shhh:

The Central Hub for DSM Community and Information

Horrible Idle Problem

DSMKevan

CurtTSI

DSMKevan

racer

DSMKevan

CurtTSI

DSMKevan

CurtTSI

DSMKevan

CurtTSI

markGSX

white1997gs

white1997gs

racer

DSMKevan

DSMKevan

SpeedFreak03

DSMKevan

TalonTSIYHL

TalonTSIYHL

TalonTSIYHL

td06hkiko

AWDPSI

TalonTSIYHL

DSMKevan

Similar threads

Latest posts

Build Thread Updates

Vendor Updates

Latest Classifieds