Problem with IAC

NewEdgeSC

Registered User
Ok we'll those of you who remember me will know that I was doing an sc swap on mustang, well I haven't been able to get my idle right even with a custom tune. My tuner told me that I need the numbers off of a 1990 SC PCM so he can tune in the correct values. Does anyone have one lying around they can give me the numbers off of?
 
Ok we'll those of you who remember me will know that I was doing an sc swap on mustang, well I haven't been able to get my idle right even with a custom tune. My tuner told me that I need the numbers off of a 1990 SC PCM so he can tune in the correct values. Does anyone have one lying around they can give me the numbers off of?

"The" numbers? Which ones would be those? Do you not have the PCM for this motor? IF not, did you not get the base configuration file from someone to load onto the EEC-IV? What is your tuner starting with as a base?
 
It's the 4 digit code on the PCM, something like AOHO or X1A2. It's simply tuned as a supercharged 3.8, he didn't use values from an SC as the base. No need to. Same as putting a supercharger on a mustang. The tune is great and the car runs perfect, it just idles high.
 
It's the 4 digit code on the PCM, something like AOHO or X1A2. It's simply tuned as a supercharged 3.8, he didn't use values from an SC as the base. No need to. Same as putting a supercharger on a mustang. The tune is great and the car runs perfect, it just idles high.

If it is a stock 1990 Automatic SC the strategy is typically GURE. The Catch code is on a label on the processor. C0S is most likely. Most people putting superchargers on a mustang put on vortech or paxton units, not MN12's. The SC intake manifold has different volumes than the stock mustang manifold as well.

For high idle I would start with making sure the idle is setup properly mechanically and that there are no vacuum leaks. There is effectively no difference between how it works on a Mustang vs the Tbird (assuming the mustang is distributorless). The configuration values are likely different since the intake manifold volume, cam, head flows rates, throttle body volumes are different for the SC. (looking at the SC strategy there are 57 Scalars related to idle, 16 graphs, and one table)

A simple google search found this information that may or may not be accurate showing the catch code indicating what Strategy.

GURE = A9U2, C0S(Auto), L0E1(Manual)
GSALC = W1M
GSALI = M2Y, Z1Z2, U2Y, S3S, X1A2
CZAWO = T4J1, W4D2

I don't know if you have noticed or not, but there is no such thing as a simple supercharged 3.8.
 
Last edited:
This project has been interesting to say the least .

If I unplug the iac and use the base idle screw for adjustment it idles just fine. I have been driving it like that for a while, I just has to warm up before it will idle. Even with the idle screw set to the lowest throttle angle it idles at over 1500 rpm with the Iac plugged in. I was going to just use the mustang iac but the plug hits the supercharger housing. I rigged it up one time with the mustang iac and it ran perfect but I had the wires pulled out of the connector and just stuck them on the pins of the iac. I just don't want to rig, I would rather do it right.
 
This project has been interesting to say the least .

If I unplug the iac and use the base idle screw for adjustment it idles just fine. I have been driving it like that for a while, I just has to warm up before it will idle. Even with the idle screw set to the lowest throttle angle it idles at over 1500 rpm with the Iac plugged in.

Vacuum leak for sure. As was mentioned it could be the idle air control solenoid has stuck open. They are available in the aftermarket to replace it.
 
Back
Top