IAC Ohms - Help!

[section525]

Okay.. my girlfriends '98 Sport SOHC has a very rough idle at start-up. So I cleaned the IAC and MAF... but no fix. In the manual it says that the unit should be replaced if the ohms are not in the 7-13 range. Her measured at a whopping 2.5ohms. So I thought, theres the problem. But I then measured the ohms in my '96 5.0 and it was just under 5 ohms.. and it runs fine.

So my question is... is the IAC not the problem? Or do both our IACs need to be replaced? WTFudge? Could that extra 2.5 ohms make mine work still and not her?

Thanks!

 

[Opera House]

I remember a while back

reading about 20 ohms on mine. It should be noted that there is an internal kickback diode in the IAC that can go bad. Did you read this with a digital voltmeter, somehing that can really read 2.5 ohms? be aware that if you test this on a bench, this is a polarity sensitive device because of the diode and you can burn it out if it is hooked up backwards. A meter has too low a voltage to detect the diode which requires 0.6 volts before it conducts. If real, the resistance is too low.

 

[section525]

Well I read in the manual how to test it and which prong the positive goes on. The meter was an analog one (with a needle). It said:

To Test:
1. Turn the ignition switch to the OFF position.
2. Disengage the wiring connector for the IAC valve.
3. Using an ohmeter, measure the resistance between the terminals of the valve.

NOTE- Due to the diode in the solenoid, place the ohmeter positive lead on the VPWR terminal and the negative lead on the IAC terminal.

[INSERT PRETTY PICTURE]

4. If resistance is not 7-13 ohms, replace the IAC valve.

So thats what I did. And obviously I am not an electronics person... but I think I did it right.

 

[Opera House]

Your method is fine

Just your meter isn't very accurate. That is why the preference now is to use the digital meters. Even the $10 ones are 1% accurate. And a comparison of a known working part with another is very valid. Wanted to make the point that many slenoids now have the built in diode and when some people bench test them with a battery to see if there is any sticking. Some real damage is done if they get hooked up backwards. Electrically the IAC is probably fine.