Horrible Idle Problem

[DSMKevan]

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

 

[driftingtalon]

i had the same problem a while back and it was my ISC http://dmtalon.v8eaters.com/ISC.html has some good stuff on it, just take it out and clean the part that was inside or whatever and then put it back in and see if that works. mine had a bunch of black stuff all over it. if that doenst work test the 6 pinsand dont buy something from the mitsu dealer, goto a junk yard they will hook you up alot better. just my two cents

 

[realitytb]

i dont know about the smoke, but the idle problems could be a vacuum leak? Im not sure about this ISC stuff...

 

[driftingtalon]

i just remembered on the TB there is a bolt with a gasket under it, sometimes this causes a bad idle because the gasket dryrots basically might wanna check for that too

 

[DSMKevan]

Errmmm checked the ISC a while ago, 0 ohms on EVERY connector *shats pants*
Ill be looking for a cheap ISC now... :thumbdown

 

[mr2gixxer]

DSMKevan- Is your car running in good working order now? I've had the same problems as you and trying to pinpoint problem. Let me know via email at [email protected] you can also IM me at mr2gixxer. Thanks.

 

[DSMKevan]

The idle problem has dissapeared, sometime near the time I checked the ISC and it was at 0. Im guessing after the ISC died, it ended the problem. I bought a new ISC anyways, since it supposedly runs in closed loop without the ISC.

I would try unplugging the ISC, and drive it around the block. If that doesnt affect the problem at all, try this:

http://www.dsm.org/how-tos/tttt/tttt3.html

Heres how to check your ISC. Make sure you test the ISC plug..not the one coming from the car... thats what I did at first :laugh:

http://dmtalon.v8eaters.com/ISC.html

 

[DSMKevan]

Got the new ISC awhile ago and put it in. It still idles a little wacky and had some stalling problems yesterday. But then again, its not nearly as bad and the BOV is still being vented (big no no). Im going to recirculate the BOV, block off the EGR, and eliminate all the other emissions crap, as well as adjust the BISS screw. Hopefully that gets rid of my idle problems.

Oh yeah, the car also stalls sometimes when you downshift. When you rev it from a stop it goes up, falls down to 600 (sometimes stalls if you rev really high), then slowly moves up to 1200-1500.

 

[TalonR]

I didnt read this anywhere.....Do you test the plug or the connector on the ISC. I am guessing the connector, cause if you test the plug it wouldnt really test anything with the ISC. I could be wrong though......So which one is it??

 

[94EclipseGST]

DSMKevan,

I had the exact same problems as you. I tested my ISC, bought a new one, replaced it, still had problems although not as bad. The car smelled rich, and the exhaust was a little sputtery. I checked my timing and that was the problem. Once I adjusted timing, all problems went away.

Give it a try and see what happens.

 

[TalonR]

Yeah, I tested my ISC today and it was bad. I will be changing this soon, after that I will have to check my timing also...

 

[DSMKevan]

Right, that could be part of the problem too. It still stalls, but only after you run it alot, and it doesnt happen NEARLY as bad as before. I'll check the timing. Could I do that with a datalogger, like the timing advance?

You should test the connector coming from the ISC. Its kind of tied onto the throttle body so you should be able to find it. I believe its the female connector. If you do happen to test the car side plug it will probably put out 5 or 50 ohms (I forgot which one), thats what mine did.

This thread is actually kind of helpful now

 

[94EclipseGST]

You should not check timing with a datalogger plugged in--it will give you an incorrect reading.

To check the timing, use a timing light.

Here is a helpful link:
http://www.plymouthlaser.com/timin.htm

 

[TalonR]

I unplugged my ISC today just to see how it would react. It seemed like it held idle decent, but still after it warmed up it started jerking at lower rpm idles while moving. It almost seems like it is missing at a few intervals while at RPM's like 2,400 in like 3rd or 4th gear.

Dont know if anyone is having simular problems, but if they did and fixed it please let me know. This is more annoying then the stupid idle surge.

Any ideas are also helpful. I just cant ever seem to get a step ahead with this car. I fix, more problems, fix again, more problems, but I will win one day

 

[DSMKevan]

I think the ISC also helps to prevent "bucking" when letting off the throttle so that could be because of the ISC. Did it do that before?

 

[TalonR]

It didnt do it that I can remember, so I guess that I am going to replace the thing and cross my fingers. Thanks

 

[DSMKevan]

It should be very easy to find a 91-99 ISC. I got "lucky" with the 1990 year, and it was very hard to find one.

 

[DSMKevan]

Jsut recently put a BOV recirculation tube on, since the car didnt come with one. It runs SOO much better, I highly advise to NOT vent with a 1g BOV on a 1g.

With the 2.5in exhaust in as well, the car seems to pull much more and idles even better ( the old exhaust leaked in the flex pipe). I really want to see how the car pulls when I get the 190 pump in and up the boost! Bye bye civics haha

 

[94EclipseGST]

Yes, never vent without a MAF/MAFT, or your car will run crappy. And even if it doesn't have idling problems, you will have crappy gas milage and less power.

 

[dsm dominator]

i have a 91 eagle talon

and i am having the same sypmtoms the bad idle rich smelling bucking crap,


could a bad o2 sensor and or clogged/ broken cat?


also about the cat,
whenever i come out of a right turn i hear a noise similiar to jigglind a penny in a beer bottle, i can stop it if I jerk the car left,

broken cat? or is my wheel bearing getting REALLY bad?

thanks for the help

--dsm dominator

 

[DSMKevan]

If its bucking alot, you either have bad throttle control or your ISC is going. If its smelling rich and running rich, its your 02 housing. Thats how the computer detects the a/f ratio (well, estimates) and tunes accordingly. Our old cars usually need new ones, since they die easily. The ISCs arent very durable either.

 

[dicion]

Dont forget ECU failure

Sorry to sound like a broken record, but these symptoms were close to mine, and my ECU caps had exploded all over everything. Just pull the ECU and inspect it. it's a 5 minute job, and might save you hours of headache. I replaced the 02, the TPS and the ISC before I pulled the ECU... well at least theyre all new now

 

[BOBS90TURBO]

Yea, Thats true about the ecu's, I had one go bad on my first dsm and it took me months to figure out the ecu was bad, it affected my idle, motor ran hella rich and was missing, hell the car ran better with the mass unplugged.

Anyway I was going to add that I was having bad idle surge and bad,rough shitty idle,, running super rich, exhaust poping at idle and it ended up being a bad intake manifold gasket leak and a bad biss O-ring gasket(even though it was new) the intake gasket was hard to hear sucking air, you have to get a long piece of vac line and put one end in your ear and run the other along the area were the gasket sits, if it leaks you will hear it.

Good Luck Ya all

 

[DSMKevan]

Yeah, dont forget about leaks. Check the VFAQ, they have a tutorial on how to make a leak tester. It plugs right onto your turbo, then you pressurize the system and listen for leaks. I should really do that, along with the ECU check.

Oh yeah, I also replaced my valve cover gasket that was cracking along with the PVC valve which was clogged.

For soldering on new ecu caps, is it tough? I have some soldering experience, but not with circuit boards. Hell, might as well get the ecu socketed when its out too.

 

[dicion]

For soldering on new ecu caps, is it tough? I have some soldering experience, but not with circuit boards. Hell, might as well get the ecu socketed when its out too.

Personally, I dont think so, even for people with little soldering experience. Its not like you're running new traces or anything If you don't have any soldering experience however, then don't attempt it as your first ever soldering attempt

I ordered the caps from digi-key, and the shipping cost more then the parts.. But the caps i got are rated 2000 hours at ~240 degrees Farenheit.
2000 hours at 45mph avg speed.... == 220k miles I think that will be good enough for the remaining life of my car

 

[DSMKevan]

Could you write up a diagram for this? I dont quite understand how to wire it up.