I was trying to set the base idle as instructed on the modular mustangs website and it tells me to disconnet the iac and start the engine. One problem the engine wont start with the iac disconnected. Any ideas on why im not having any luck? Could their procedures be wrong?
Start car until it reaches opertating temp
Unplug IAC wiring
Set idle to your spec
Plug in IAC wiring
Turn car off and with key on and engine off check TPS setting
Reset TPS as needed
This has always worked for me.
Others may have different technics but this should get you close
1. The car must be at operating temps. If you can't keep it idling, drive it until it reaches full water temp.
2. Turn ON the headlights.
3. Turn OFF any accessories, like a/c, heater, defrost.
4. Unplug the IAC connector. The IAC is the small cylinder attached to the throttle body.
5. Adjust the throttle stop screw until you have the idle rpm you desire.
6. Plug the IAC connector back in.
7. Recheck the TPS voltage, since you may have changed the throttle blade position.
Note: If you unplug the IAC and the engine stalls, then you know the idle rpm was probably too low. Leave everything as is, just open-up the throttle screw a bunch so that the engine can breathe while you set the idle rpm. Restart the car, and lower the idle rpm via the throttle screw. Now plug the IAC back in.
'94-'95
Begin with a cold vehicle. The idea here is to get the car to a firm cold idle with enough air bleed capacity left in the idle circuit for IAC adjustment.
The idle stop should be set first. Back out the idle stop screw, away from the bell crank arm, until about 1/2 turn past the point where it no longer makes contact (blade fully closed). Using an 0.010" feeler guage, tighten until gauge just drags between screw and bell crank arm. Remove feeler gauge. Tighten screw exactly 1 1/2 turns. If the screw is very loose, put a drop of loc-tite or silicone on it, so it doesn't work out of adjustment.
Now remove the connector to the Idle Air Controller (IAC) just on the other side of the throttle body. Start the car and allow vehicle to warm for 2 minutes. Give a small "blip" to let it settle. If it is having a hard time staying running you may have to get an assistant until you can get to the front of the car. Now open or close the air bleed screw (CCW opens) next to the IAC until the car idles at 575 to 600 rpm. For guys with aftermarket cams and an EEC tuner, you might want to idle a bit more briskly, say 650 to 675.
Obviously, this rpm range is by what the car and driver wants...IE, no set idle speed, whatever works for YOU.
Turn off the car. Now count the number of turns clockwise to close on the idle air bleed screw. If it falls between 1/2 and 2, it's okay, now reverse it out the same number of turns. Log the number somewhere in case you need it for the future. Reconnect the IAC. You are done.
If the air bleed screw is above 2 turns, it's a good idea to tighten the idle stop screw another 1/2 turn, then repeat the idle setting. If it is below 1/2 turn, then loosen the idle stop screw by 1/4 to 1/2 a turn, and repeat the idle setting. Be sure to put another drop of silicone RTV on the stop screw if it was disturbed. Reconnect the IAC. You are done."
with so many variations of instructions how does a person know he is doing it right? at what step the computer actually reset the idle? when you disconnect the iac with the engine running?
There are variations to accomodate people with mods.
The GW342 method above should take care of it.
When you try and do this on a cold motor, it will stall. The IAC's duty cycle is 100% at start up, and it is needed for proper cold idle (like a choke on carbed cars).
The computer and IAC together will make adjustments to the idle depending on the demand. I thought you were trying to set base idle. The write up that RacEoHolic330 provided is very detailed and should be the basis to follow. Computer will then provide adjustments after you complete those steps.You wont do any damage to the car performing the steps provided. Why are you needing to set the idle?? Have you changed something?