IAC motor will not move
11-03-2008, 07:39 PM
#1
IAC motor will not move This is a copy of what I posted in the hptunners forum. Any help would be great.
Ok so I have been having issues with cold start idle and all that and have been back and forth with my tunner trying to make changes so it would idle. Now 2 weeks ago my car started to surge and car on and not it idling high and will not idle down until the PCM pulls all the timing. and this is not good. So I traced it down to what I thought was a bad IAC motor that would not move. So I swaped out an IAC motor that was known good. (now when I swapped them the new one was extended more so I know it was closed more. now my car idles at a good speed but I still have my cold start issue. And comanding the IAC steps with the scanner I can't get my idle speed to change. I brought home an IAC noid light thing and it does not flash at all like it would on any other car. Now I need to go back with my lap top and try to commande it to move and see if the lights flashes. Anyways my question is there anything in the tune that would make te IAC motor not work? or could I have a bad PCM
Any ways the car has an LS6 intake and stock TB with NO drill mod got the car to idle with set screw. Also it is a D1 procharged 347 with a 224/232 595/583 114lsa cam with a 2 bar tune. Thanks for all help in advance. Also I can post up the tune if need be.
Ok so I have gone as far as looking at commanded vs actual and commanded and acual change when I comand it but my idle will not change and if I out the noid light/IAC tester in place of the IAC motor it does not light up at all. I guess my next step is ohming all the wires out the only thing left would be either the tune or the PCM itself.
Ok so I have been having issues with cold start idle and all that and have been back and forth with my tunner trying to make changes so it would idle. Now 2 weeks ago my car started to surge and car on and not it idling high and will not idle down until the PCM pulls all the timing. and this is not good. So I traced it down to what I thought was a bad IAC motor that would not move. So I swaped out an IAC motor that was known good. (now when I swapped them the new one was extended more so I know it was closed more. now my car idles at a good speed but I still have my cold start issue. And comanding the IAC steps with the scanner I can't get my idle speed to change. I brought home an IAC noid light thing and it does not flash at all like it would on any other car. Now I need to go back with my lap top and try to commande it to move and see if the lights flashes. Anyways my question is there anything in the tune that would make te IAC motor not work? or could I have a bad PCM
Any ways the car has an LS6 intake and stock TB with NO drill mod got the car to idle with set screw. Also it is a D1 procharged 347 with a 224/232 595/583 114lsa cam with a 2 bar tune. Thanks for all help in advance. Also I can post up the tune if need be.
Ok so I have gone as far as looking at commanded vs actual and commanded and acual change when I comand it but my idle will not change and if I out the noid light/IAC tester in place of the IAC motor it does not light up at all. I guess my next step is ohming all the wires out the only thing left would be either the tune or the PCM itself.
11-03-2008, 08:30 PM
#2
The IAC has a number of parameters that must be met for it to operate (in closed loop). For some reason we do not get to edit those parameters or even see what they are. I have seen more than one PCM lose it's IAC output, but I wouldn't jump the gun on that unless you have a spare laying around that you can try. I know that, at least for the 98s, if the voltage seen AT the PCM drops below 9.5V, the IAC will fall out of closed loop and not update (change position).
Last edited by Frost; 11-03-2008 at 09:18 PM.
11-03-2008, 08:47 PM
#3
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I recently was trying to get the blower truck to idle
lower and getting no satisfaction from bidirectional
controls. I hooked up my Camaro IAC motor to it,
off-the-TB, and my buddy could feel it move when
I dialed it up and down. Truck IAC would not move
the same (at all) and then abruptly fell apart. This
was a brand new IAC custom made for the 105mm
TB (though it looks like they customized it, by
taking it apart, rotating the plug in the body and
staking it with roll pins followed by some black
paint).
IAC is a stepper motor, you may not see the drive
out of the PCM to light a 'noid light and even if you
did, you'd have to pick the right phase legs and do
it while the thing is actually stepping.
Look at the IAC drive signals going by the phase
info on your schematics, you ought to see some
AC voltage when it's active. On a PCM which does
not have the drive circuitry installed (like many
electric throttle PCMs) you'll just see a few mV
of random noise. Look for winding continuity in
the phase legs in the IAC itself and active drive
from the harness.
lower and getting no satisfaction from bidirectional
controls. I hooked up my Camaro IAC motor to it,
off-the-TB, and my buddy could feel it move when
I dialed it up and down. Truck IAC would not move
the same (at all) and then abruptly fell apart. This
was a brand new IAC custom made for the 105mm
TB (though it looks like they customized it, by
taking it apart, rotating the plug in the body and
staking it with roll pins followed by some black
paint).
IAC is a stepper motor, you may not see the drive
out of the PCM to light a 'noid light and even if you
did, you'd have to pick the right phase legs and do
it while the thing is actually stepping.
Look at the IAC drive signals going by the phase
info on your schematics, you ought to see some
AC voltage when it's active. On a PCM which does
not have the drive circuitry installed (like many
electric throttle PCMs) you'll just see a few mV
of random noise. Look for winding continuity in
the phase legs in the IAC itself and active drive
from the harness.
11-03-2008, 08:57 PM
#4
Well the IAC tester hat I am using is actually plugs right into engine harnes in place of the IAC motor. I have used it before on stock non modified vehicle using s TECH2 and have seen it work but for some reason I can not get it to work with my car. I will have to try with my truck and my hptuners.
If I know the PCM is the problem I can get a new one for my car. I work at a Dealership in the Service department and I am still under the 8/80 warrenty for the PCM.
If I know the PCM is the problem I can get a new one for my car. I work at a Dealership in the Service department and I am still under the 8/80 warrenty for the PCM.
