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Thanks for the clarification on the measurement. I will grab a spare one I have, do some measuring and edit the original post as needed to clarify. I believe I took my info from the manual.

-SP
It's 1-2, 2-3, 4-5, 5-6. I used to test these things all day long. Now, if I receive an aluminum ISC, I just throw it in a box. I don't even bother anymore, they are all worthless IMO. Testing the coils is only half the battle. Plus, you are testing when it cold... there is no guarantee it works when it's warm.

It drives me nuts when people want to skimp on something like this. 80% of the aluminum ISC I receive are bad. I seriously have a large flat rate box FULL of them. So statistically speaking it's not a matter of "if" but "when". And a failing ISC can take out your ECU, if not dealt with in a timely manner. So quit being cheap (not pointing out anybody in particular BTW) and buy a new aftermarket or OEM ISC.

Aftermarket ISC part number is AC99 (you can find these for $50 shipped)
OEM ISC can be bought here: http://www.dsmisc.com/dsmweb-dw/index.html

The coils on the ISC below tested within specs. Then I decided to open it up.



 

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WOW! …April…That confirms the old saying…Picture is worth a thousand words.
 

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Yeah I don't know because that was actually came off a TB that a member sent in for a rebuild. IIRC, the throttle body was rather clean. You would be surprised what can come out of the throttle body. I had one where the lower portion (the FIAV) was FULL of oil.

My point being, it's a 20+ year old electrical component that is notorious for failure. That was the first thing I replaced on the Spyder just because of the known issues. Had one go out on the 1994 with less than 50K miles. I see people doing five figure builds using an original ISC, it just boggles my mind LOL.
 

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Wheee! 2 wheels is fun!
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Discussion Starter #45
I dont understand is why people STILL look for a screw to change their idle speed when IAC's have been on fuel injected vehicles since the mid 80's! It shouldnt be a mystery, but it may be the reason April sees this part being ignored all the time.

Maybe I should delete this thread and keep the "secret." :)

-SP
 

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Well now-n-days on these cars... it's a multitude of things that can cause idle issues. The two culprits are vacuum leaks and ISC. Between dried out vacuum hoses and seal, and here so lately, FIAV don't function properly... it hard to track down the issue without giving somebody a checklist.

Here I'll start with a checklist:

1. Open up your ECU (mainly 1st Gens 91-93)
2. Test/Replace your ISC. (I would just replace it if you can afford it)
3. PRESSURE test, Pressure test, pressure test
4. Fix all the leaks you find with pressure testing
 

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Lots of good info here
I had a problem with some low rpm hesitation, decided to clean the IAC/Throttle body, I used just a non-solvent carbon/oil cleaner, sprayed some in the IAC hole, next step was the IAC disassembly, 2nd gen or plastic type, it was really clean, tested the coils, about 50 ohms but still worked, I reinstalled the IAC and let the car sit overnight..

Next day, on my way to work the car was stalling at every stop light! I managed to get to work, later I checked everything that is common to stalling, didn't touch any gaskets or the BISS so I was sure that it wasn't a vac leak, maybe some water got inside the IAC well.. looked like new, I tested again the coils, reinstalled the IAC but.. I contracted the pintle, all the way down (allowing maximum airflow?), when I started the car the RPMS spiked up, about 2k!

That seemed weird, I remember the Jeff Lucius writeup, he recommend backing up the pintle halfway:

Before putting the two halves together, I rotated the lead screw so that the pintle was in the middle of its range of motion. I am not sure if this accomplished anything positive or not. I suspect the ECU tests the servo by retracting and extending the pintle to correctly index the steps.
Did that, now the car get proper idle speed, I know the IAC is working because of the RPM increase with AC/Power Steering load.

Now the question, how can you know when to calibrate the pintle? Every start up, when battery terminal is removed? How do they come when new, half way?
 

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Discussion Starter #51
It doesnt need any "calibration." Its supposed to move to keep the idle at the right speed even though the load at idle changes. I'll guess that your pintle was stuck and when you moved it it became free and could do its job.

-SP
 

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Most likely, I never had to do that between IAC swaps.. also the pintle didn't felt like it was stuck (also tested the "steps" with a 5V source)
 

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Plus, you are testing when it cold... there is no guarantee it works when it's warm.
This is so true. My car (1994 Dodge Stealth R/T) kept stalling at idle so first thing I did was pull my IAC and test the resistance at each coil. Sure enough, each read about 30 ohms. Opened the IAC up and it was perfectly clean. No corrosion at all.

HOWEVER, I vaguely remember somebody (on some other thread, can't remember which) saying they took a hairdryer to their IAC to heat it up and then tested resistance at each coil again, so I tried that. Sure enough, after heating it up, the first coil showed an "infinite" value on my multimeter, whereas when it was cold, it read normal.

To make a long story short, April hit the nail right on the head here. If your IAC is showing normal resistance while it is cold, warm it up with a hairdryer and try again. You might have different results.
 

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Do you know if it's a function of the IAC to keep idle high when moving? I've had my TB rebuilt by April and I tested the IAC as good a while back, and she tested it good as well. Everything idles nice and smooth, nothing weird about it. Except, it starts to idle really high until about 5-10 mph after a while of driving it. It has to cool down and be a while to stop doing this (i.e., no turn off and on real quick to fix it).

I know ECU is good (new Chrome) and no leaks (tested). Only other thing I can think of is the IAC. Throttle isn't stuck (TPS reads ~13 (exact same as idle), but I can even feel it pulling the car along if I'm coasting in gear. Car revs to this high idle (1800-2300) during shifts, too. Drives me crazy.
 
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