Tried the IAC mod
06-13-2007, 05:28 PM
#1
Thread Starter
Join Date: May 2007
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Posts: 21
Tried the IAC mod
I've been having a problem with my rpm's hanging around 1800-2000 for several seconds and then dropping down to 1100 (note: I put some u/d pulley's and a new tensioner on a few weeks ago). I read on here that you can modify the gasket on the IAC. I did that (made sure to disconnect the neg. terminal) and the rpm's still hang at like 1400 for several seconds and then drop to about 1000. After driving it for around 15min, the check engine light came on. Although it's idling a lot better now, it's still idling too high. Any suggestions on why the CEL came on or why it's still idling high? The new hole in the gasket is pretty small, so I don't think it needs to be smaller. Would a new IAC eliminate this problem? Thank you much for the help!
06-13-2007, 08:00 PM
#2
4th Gear Member
Join Date: Jul 2006
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Posts: 1,399
RE: Tried the IAC mod
You must of read that IAC mod thread. I think that was one of the things that just about everyone who read it went out and tried it including me. I would be willing to bet the whole is too big. What size bit did you use? I first used a 3/16 and it idled high then I stepped it down and it is perfect now. It's kind of a trial and error thing because different cars idle differently so not every car is gonna idle at the same speed if they are using the same size hole even if they are the same exact car. I made several of the gaskets before I got it right. I should of just started real small then I can make it bigger if need be. I started out too big so had to make a brand new one[:@].
No idea why a cel came on though
No idea why a cel came on though
06-13-2007, 10:07 PM
#5
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RE: Tried the IAC mod
if the hole is too big, it could be screwing up your A/F ratio could be running too rich or lean now. this is why i didnt do this mod, i can deal with hanging rpms.
06-13-2007, 11:34 PM
#7
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Join Date: Aug 2006
Location: Orange County, CA
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RE: Tried the IAC mod
Yeah I had the same shyt happen to me. My CEL came on, and it was a code saying the IAC was acting up. I cleared the code, and went back into the garage to mak a new gasket. This time, I disconnected the negative batt. terminal for about 30 minutes, and made a smaller hole, (I had a 3/16" but it was too big, high idle, so I went down one whole size) It works perfectly now. Although, it sputters for a few seconds after a cold start, it drops revs really fast.
Try making a hole one size SMALLER than the 3/16", sorry I forgot the measurement. And take off the neg. batt. terminal abotu 15 minutes before you even start opening stuff up and making a new gasket. OH! And DO NOT over tighten the bolts holding the IAC valve.
Try making a hole one size SMALLER than the 3/16", sorry I forgot the measurement. And take off the neg. batt. terminal abotu 15 minutes before you even start opening stuff up and making a new gasket. OH! And DO NOT over tighten the bolts holding the IAC valve.
06-14-2007, 04:58 AM
#8
Join Date: Jul 2006
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Posts: 42
RE: Tried the IAC mod
The exact same thing happened to me. I installed my pullies and TB/plenum and my idle would hang as high as 1700 before dropping to around 1200. The RPMs would fly up between shifts too. I tried the IAC mod with several different hole sizes. 3/16" worked a little bit better, but it threw a CEL. At that point, I made a visit to the local Mustang tuner and bought an Xcal2. The car runs perfect now. [8D]
06-14-2007, 06:15 AM
#9
6th Gear Member
Join Date: Jan 2004
Location: United States
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RE: Tried the IAC mod
I am going to have to see some very relialble proof before I beileve that disconnecting the battery for longer than say 10 seconds does anything compared to disconnecting it and the putting it right back on.
there are no large caps etc in the ECU, and its not like its going to slowly drain out over time... its not water
there are no large caps etc in the ECU, and its not like its going to slowly drain out over time... its not water
06-14-2007, 06:52 AM
#10
TECH SAVANT
Join Date: Dec 2006
Location: Saint Augustine, FL
Posts: 10,938
RE: Tried the IAC mod
The factory workshop manual (quoted below) actually says a "miniumum of 5 minutes", however most installtion docs for TBs, plenums, and the like will say 20 minutes. [/align][/align]"Large caps" is a relative term, when you have something like a small CMOS RAM that only draws 1uA or less a tiny 10 uF "capbattery" is relatively huge...[/align][/align]
[/align] [/align][/align](edit) I suspect this is quite deliberate to allow time for swapping out the battery, etc. without resetting the KAM and potentially causing drivability "call-backs" 'til things get relearned...[/align]
Resetting Keep Alive Memory (KAM) [/align][/align]Resetting Keep Alive Memory will return PCM memory to its default setting. Adaptive learning contents such as idle speed, refueling event, and fuel trim are included. A PCM Reset (described above) is also part of a KAM Reset. Both can be useful in post repair retest.
After Keep Alive Memory has been reset, the vehicle may exhibit certain driveability concerns. It will be necessary to drive the vehicle to allow the PCM to relearn values for optimum driveability and performance.
This function may not be supported by all scan tools. Refer to scan tool manufacturer's instruction manual.
If an error message is received or the scan tool does not support this function, disconnecting the battery ground cable for a minimum of 5 minutes may be used as an alternative procedure.
After Keep Alive Memory has been reset, the vehicle may exhibit certain driveability concerns. It will be necessary to drive the vehicle to allow the PCM to relearn values for optimum driveability and performance.
This function may not be supported by all scan tools. Refer to scan tool manufacturer's instruction manual.
If an error message is received or the scan tool does not support this function, disconnecting the battery ground cable for a minimum of 5 minutes may be used as an alternative procedure.