Is there a way to test the IAC?
06-27-2010, 08:42 PM
#1
Is there a way to test the IAC? I've got a 99 LS1 in my BMW 325i. I finally started it and it idles at 2500rpm. I determined the Idle Air Control valve want working. I pulled it apart and everything is free moving. My father just bought a low milage '98 LS1 that has been sitting for 5 years. I stole the throttle body off his engine and put it on mine and it wouldnt idle at all, I had to hold the throttle open some for it to run. My fathers engine is on the engine stand, so I dont know if it runs right or not. I guess its possible that I have 2 bad IAC's... is there a way test them or a way to check the harness to make sure its getting the power it needs to work.
thanks
thanks
06-27-2010, 09:36 PM
#2
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yes use a multi meter to test the harness. if you had a scan tool you could check the iac counts. did you do any thing before it started to idle high or did it just happen one day?
06-27-2010, 09:44 PM
#3
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Do you have tuning software?? With efi live you can command the iac counts, or rpm. If those change the wiring and valve itself are working. The gm tech 2 will do it as will some other aftermarket scantools. I have a otc iac harness tester set that I can also hook to bat then to the sensor and move it my self, (doesnt test the cars wiring, but it is quick and easy when you need it.
06-28-2010, 03:50 AM
#4
Are you sure the throttle plate is closecdf all the way?
Look at the front of the throttlebody and find the passage the goes to the IAC, put a piece of tape over it to prevent the air from going in it, then start it and see if it still idles high. If it doesn't you know its IAC related, if it still does, toy need to find the vacuum leak, thats letting the excessive air in. Both HPT and EFI have the ability to force the IAC closed, IIRC, you can issue this command with just the key on and the motor not running, that way you can have the IAC out and watch it. KD Tools (and I'm sure others) makes a trester to plug the harness plug in, it tells if you're getting a valid singal.
Look at the front of the throttlebody and find the passage the goes to the IAC, put a piece of tape over it to prevent the air from going in it, then start it and see if it still idles high. If it doesn't you know its IAC related, if it still does, toy need to find the vacuum leak, thats letting the excessive air in. Both HPT and EFI have the ability to force the IAC closed, IIRC, you can issue this command with just the key on and the motor not running, that way you can have the IAC out and watch it. KD Tools (and I'm sure others) makes a trester to plug the harness plug in, it tells if you're getting a valid singal.
06-28-2010, 09:53 AM
#5
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Not all PCMs have the IAC driver components in them.
If you measure individual IAC legs to GND, a functional
PCM will show some voltage while one with missing IAC
drivers will show only millivolts of electrical noise.
All cable-throttle PCMs (F-bodies, early trucks, vans)
should be OK bus a large portion of DBW ones, saved
a couple of bucks on components.
If you measure individual IAC legs to GND, a functional
PCM will show some voltage while one with missing IAC
drivers will show only millivolts of electrical noise.
All cable-throttle PCMs (F-bodies, early trucks, vans)
should be OK bus a large portion of DBW ones, saved
a couple of bucks on components.
06-28-2010, 10:19 AM
#6
Not all PCMs have the IAC driver components in them.
If you measure individual IAC legs to GND, a functional
PCM will show some voltage while one with missing IAC
drivers will show only millivolts of electrical noise.
All cable-throttle PCMs (F-bodies, early trucks, vans)
should be OK bus a large portion of DBW ones, saved
a couple of bucks on components.
If you measure individual IAC legs to GND, a functional
PCM will show some voltage while one with missing IAC
drivers will show only millivolts of electrical noise.
All cable-throttle PCMs (F-bodies, early trucks, vans)
should be OK bus a large portion of DBW ones, saved
a couple of bucks on components.
Is it a Blue / Red plugged PCM? If so, you shouldn't have an issue.
If its a Blue / Green plugged one you might.
Since he said 99 I assumed it was a Blue / Red plugged one, but he never said it was
If its a Blue / Green plug one list the service number
