IAC Signal
08-06-2010, 02:59 PM
#1
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IAC Signal Since the first start up on my ls1 conversion on my 2nd gen camaro I´m having problems with the IAC valve and Idle, it stays up 1800-2000 rpm, never goes down. Change the IAC valve (installed a new one) and scanned the engine yesteday, and realiced that there is no signal to the valve, always shows 0 or litle movemment but alway stays in 0 value. Maybe some cut wired? PCM problem?. I manually taped the TB IAC air hole. and idle speed goes down >> IAC valve problem? It is the only problem left to finish conversion... (I guess 
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08-06-2010, 04:34 PM
#2
it's at zero because it's trying to lower idle but it's run out of room to do so. Either the blade is open too far on the throttle body, or there is a vacuum leak. What you are describing is what the IAC should be doing during either of these conditions as well.
08-09-2010, 08:37 AM
#3
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Just check again, did a few test:
1.- install the old IAC on the TB with spindle all out (air pass closed), and connected to the PCM. Star the engine and did not start unless I move the gas pedas (TB slightly open), check on the scan and it show it should be triying to open the IAC valve.
2- unplug the old IAC installed on the TB from the PCM and plug the new IAC to the PCM (leave it connected but not intalled on the TB) to check if it moves during the same process. Star the engine and did not start unless I move the gas pedal a little, take a look on the new IAC that was plug and it didn´t move, the scanner show it should be moving (try to put the RPM a lithe higher.
Idle was at 500-600 rpm on both cases
Conclusion:
- Cut wired
- Bad PCM IAC comand pins
- Something wrong inside the PCM that does not let the signal go through the IAC pins.
What do you think?
1.- install the old IAC on the TB with spindle all out (air pass closed), and connected to the PCM. Star the engine and did not start unless I move the gas pedas (TB slightly open), check on the scan and it show it should be triying to open the IAC valve.
2- unplug the old IAC installed on the TB from the PCM and plug the new IAC to the PCM (leave it connected but not intalled on the TB) to check if it moves during the same process. Star the engine and did not start unless I move the gas pedal a little, take a look on the new IAC that was plug and it didn´t move, the scanner show it should be moving (try to put the RPM a lithe higher.
Idle was at 500-600 rpm on both cases
Conclusion:
- Cut wired
- Bad PCM IAC comand pins
- Something wrong inside the PCM that does not let the signal go through the IAC pins.
What do you think?
Last edited by patoruzrs73; 08-09-2010 at 08:43 AM.
08-11-2010, 12:49 PM
#6
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There are two IAC phase pairs for the stepper motor.
Each leg should have some nonzero voltage to ground
as read by a DC meter. If you see tens of mV of noise
then your PCM lacks (or has busted) IAC driver circuitry.
Each leg should have some nonzero voltage to ground
as read by a DC meter. If you see tens of mV of noise
then your PCM lacks (or has busted) IAC driver circuitry.
08-11-2010, 01:47 PM
#7
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the PCM was tuned and order for a suplier, it is for a cable operated TB so it should have the IAC controls.. unless the suplier get confused.. (I guess and hope not)
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08-15-2010, 12:09 PM
#8
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I´ve check for the PCM id number, apparently when i bought this new pcm the store send me the incorrect one, the DBW version instead of the DBC.. we will change it and see what happends... anyway the store is very responsable and asume their mistake.. I´m really happy with their response..
