IAC count on modded engines
Thread Starter
Le Mans Master
Joined: May 2004
Posts: 5,866
Likes: 60
From: Hellinois
Finalist 2020 C4 of the Year - Modified
IAC count on modded engines
I am trying to get my car to do something it may not be capable of now with all the mods I've done. I cannot get the IAC to close, it may fluctuate, (counts) but it will always go back to 160. I can get it to idle great but there is no IAC action when I put it in gear or turn on the a/c. I have tried setting the counts as described here on the forum but it just won't work, when I open the throttle blade a little more then rev it & let it settle down all I get is a higher idle speed.
Also I am running an LS style throttle body which has a non adjustable tps. The tps setting is right at .78 with the idle around 900 rpm. Does anybody know of a company that makes an adjustable tps for this throttle body? I have to get it down, I have a terrible dead spot just off idle. I have tried opening the holes to allow adjustment but there iust isn't enough material to get it down where I need it, I have ruined two tps's trying to slot the holes.
80 mm throttle body,
32 lb. injectors
fairly radical hydraulic roller cam,
383 cubes and all the other go fast goodies that are needed.
Also I am running an LS style throttle body which has a non adjustable tps. The tps setting is right at .78 with the idle around 900 rpm. Does anybody know of a company that makes an adjustable tps for this throttle body? I have to get it down, I have a terrible dead spot just off idle. I have tried opening the holes to allow adjustment but there iust isn't enough material to get it down where I need it, I have ruined two tps's trying to slot the holes.
80 mm throttle body,
32 lb. injectors
fairly radical hydraulic roller cam,
383 cubes and all the other go fast goodies that are needed.
Last edited by Midnight 85; Apr 29, 2014 at 10:49 PM.
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
I would think the idle would be really high with an IAC count of 160. Theoretically it could go up to 255, but I recall that mine is limited to 144 in the EPROM parameters.
LS engines work differently than L98s. The ECM reads the TPS when the ignition is turned on and remembers the reading and calls that "throttle closed". LT1s do this also, which is why the TPS is not adjustable -- it doesn't need to be.
One thing you could try is to jumper ALDL pins A & B, turn on the ignition and then unplug the IAC connector. That should cause the IAC to close. Leave it unplugged, start the engine and see what happens.
LS engines work differently than L98s. The ECM reads the TPS when the ignition is turned on and remembers the reading and calls that "throttle closed". LT1s do this also, which is why the TPS is not adjustable -- it doesn't need to be.
One thing you could try is to jumper ALDL pins A & B, turn on the ignition and then unplug the IAC connector. That should cause the IAC to close. Leave it unplugged, start the engine and see what happens.
Thread Starter
Le Mans Master
Joined: May 2004
Posts: 5,866
Likes: 60
From: Hellinois
Finalist 2020 C4 of the Year - Modified
I have done that, the idle is considerably lower with the IAC closed. I don't have a problem leaving the tps set so high but the LS ecm have a compensating feature that makes moving the tps unnecessary. If I did not have a monster bog with it set so high I would gladly leave it alone. Edelbrock's tech suggests elongating the holes so the tps can be moved so I may try that today. The car is running great otherwise but the bog is a real pia. I may also close the IAC and leave it disconnected. if that will remove the damn bog.
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
I cured my off-idle bog by fixing a vacuum leak...
Thread Starter
Le Mans Master
Joined: May 2004
Posts: 5,866
Likes: 60
From: Hellinois
Finalist 2020 C4 of the Year - Modified
I found the problem, I was thinking what it was that I had just done recently and the only thing was replace the oil temp sender,,,,, right in the same area as the O2 connector.
I looked everything all over and saw nothing so I took the O2 out & bench checked it, it was okay, (it was also almost new) I went to put it back in when I caught a glimpse of something shiny right at the connector half that is on the car. I got to looking and could not move the wire so I figured it was just shrunken insulation. I looked again and it was too shiny for that so I then looked inside the connector, (weatherpack) and the signal wire pin had somehow gotten pulled far enough out of the connector that it was not making contact. I pushed the wire back in place and made sure it had locked in and all my problems disappeared. I was just sitting down here to let everybody know what I found when I read your latest response. Thanks for the suggestions, I have everything reset and I am ready for some warm dry weather.
I looked everything all over and saw nothing so I took the O2 out & bench checked it, it was okay, (it was also almost new) I went to put it back in when I caught a glimpse of something shiny right at the connector half that is on the car. I got to looking and could not move the wire so I figured it was just shrunken insulation. I looked again and it was too shiny for that so I then looked inside the connector, (weatherpack) and the signal wire pin had somehow gotten pulled far enough out of the connector that it was not making contact. I pushed the wire back in place and made sure it had locked in and all my problems disappeared. I was just sitting down here to let everybody know what I found when I read your latest response. Thanks for the suggestions, I have everything reset and I am ready for some warm dry weather.
