Getting The IAC Dialed In But,....

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69 1/2 Six Pack Bee
Experienced MS/Extra'er
Posts: 345
Joined: Fri Aug 20, 2004 11:12 am
Location: Ontario, CA

Getting The IAC Dialed In But,....

Post by 69 1/2 Six Pack Bee »

I have started to zoom in on tuning the IAC but I am having another strange behaviour so maybe you can help me pinpoint it.

If you take a look at the settings you can see that I have quite a few steps to fully open and quite a few till closed but I tried a zillion times at different step sizes and this is what I have derived. Heres the scenario;
I have several IAC's to play with so I leave one on the TBI to block the passageway so the engine idles normally. I have another one plugged in and laying on the intake so I can see the operation. I am fully warmed up @ 180F. I turn on the key, the pintle retracts all the way in which is correct. I start to crank and it immediately moves to the crank position which I have set @ 190 so it "stages" there for 5 seconds after it starts as it should. It then jumps to 215 which fully seats the pintle (this is what it is in the housing) as expected. I can do this repeatedly and it works great.

Okay, soI know the thing is working correctly. I now put the IAC into the TBI and re-start the engine a few more times and it works just as expected. But now, I stop the engine, swap in another coolant temp. sensor, drop it in ice cold water, (to simulate a "cold" start) wait a few moments for the temp. to stabilize, re-start the engine and it idles up to around 1350RPM and the "IAC Steps" gauge in MT shows I am @155 steps just as I have charted in the table. I remove the sensor from the water and start to warm it up. I monitor the realtime window and I see the temperature increasing considerably, the IAC Steps are increasing as indicated in MT but the engine speed never changes. If, however, I shut the engine off and re-start, the engine speed corresponds to the indicated steps with respect to the decreased fast-idle speed. I can let it idle until the sensor once again reads 180F and still the engine speed will not change unless I re-start the engine. The IAC is not reacting to the change in engine temperature.
BTW, I have played with the step speed anywhere from 1.5 to 5.5 ms and it does not make a diference. I had the algorithm at "Moving Only' but it seems to work better on "Always on".

What does this sound like? Take a look at my settings and pleas tell me if I need to change any of the parameters or what else migh be happening

Thanx,
Bud.

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69 1/2 Six Pack Bee
Experienced MS/Extra'er
Posts: 345
Joined: Fri Aug 20, 2004 11:12 am
Location: Ontario, CA

Post by 69 1/2 Six Pack Bee »

I think I will just jump the resistors and try it again. Many posts have been eluded to this "fix" as well as having being suggested to me. I am close....almost there! :)
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