I'll keep it short this time

How jumpy should the voltage be to (or at)the IAC and would a bad IAC be the cause of the problem ?




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Da Boid

- 4 out of 5 people think the 5th is an idiot

 

Here's how I've heard to test the power to the IAC: touch a grounded test light to each of the four pins on the IAC connector, one by one. For each of them, the light should flash. I'm assuming that if the light is supposed to flash, then your voltage is supposed to be pretty jumpy. But I don't have any numbers.

 

Well the IAC is a stepper motor so yeah the voltage better be "jumpy"

 

LoL,,, I guess I should've been a little less vague

The idle is hunting up and down at idle & the car likes to try and die rolling to a stop w/the clutch in and does die at times.

It was finally 'warm' enough to get out in the garage so I ran the car last night I watched the voltage,, it would jump to just over 12v hold for a moment then drop to under 1v,, and did this randomly on 3 of the wires into the IAC (same jumpy voltage on all 3). When revving it would jump to low and increase in voltage with how far the throttle opened.

Is this normal for the IAC to do?
If it's not normal,, would the IAC being bad cause the problem ?

Hopefully I was a little more clear this time.

Thanks for the help guys

Another note,,, I have checked the vacuum at idle and it's pretty steady right around 19"


[This message has been edited by deadbird (edited December 27, 2000).]

 

DB,

Using a digital voltmeter to read IAC control signals is pretty much a fruitless effort. The pulses are delivered from the ECM at a rate of up to 100Hz, so most DVMs won't even be able to update the display fast enough to get any meaningful readings. And since the pulses are switching rapidly between positive and negative, the meter gets confused easily. If you have a small oscilloscope or scopemeter, you might be able to get some meaniful data.

The IAC is supposed to "park" to a near fully closed position when the throttle is opened beyond about 5% of base position. This is probably why you notice a general change in the average voltage you are measuring when the throttle is opened. The pulses reduce to about nothing for amplitude once the motor is presumed closed.

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Later,
Vader
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"No matter how hard you try you can't stop us now"
Adobe Acrobat Reader 4.0

 

Hey vader,
unfortunatly,, I don't have neat toys like an oscilliscope,,, I'm sure you've got to be sick of responding to my post by now anyways ,,,
the one thing I did notice,,, taking in to consideration what you said,,, is the IAC voltace held high voltage(5-6 seconds) w/o any variance(even .01v) then dropped and held(going up and down randomly with steady time holding)
I realize digital isn't the most accurate,,, but mine is fairly responsive (as fas as quartz display goes) but the voltage(seems) goes up smooth (cracking throttle slow) when revving the motor.
I don't mind spending the $ on the IAC to replace it,,,but does this sound like the problem or could it be a different gremlin ?