If you recently added some bolt on parts, disconnect the negative battery cable for 5 min, tap on the brake pedal so all residual power is depleted. Then reconnect the battery cable.
This will allow the computer to relearn where your idle should be.
You are not supposed to adjust the idle...your EEC is set to a specific voltage sent by the TPS, you mess with the throttle position, you mess with EEC=poor performance.
Yes, you can adjust the idle, although you should not have to. If you medded with it already then you need to reset the base idle. Or, if you added a new TB, you make have to reset the base idle. Here is how you do it:
1 - Remove the electrical harness from the IAC. Make sure all electical items are turned off.
2 - Start the car. If it dies without hitting the gas, the "base idle" is set too low. If this happens, adjust the idle screw on the TB slightly and try again.
3 - Keep repeating until the car just barely runs without stalling.
4 - If the car idles the first time, then try turning the idle screw back while the car is running until it starts to act like it is going to stall.
5 - Running the car with the wire harness on the IAC removed will cause a SES light. You can discharge the car battery and restart. This will reset the SES.
DBMSTING: You are wrong! That is what the idle set screw is for on the TB. Those instructions come directly from Brian at CJ Pony in Harrisburg, PA. He is the shop supervisor at an all mustang performance shop. The TPS simply reads the position of the TB and sends this data to the cars computer. The above instructions are for setting the base idle on the vehicle. Once the base idle is set correctly, the car adjusts the idle from there based on engine load and ambient conditions.
DBMSTING: You are wrong! That is what the idle set screw is for on the TB. Those instructions come directly from Brian at CJ Pony in Harrisburg, PA. He is the shop supervisor at an all mustang performance shop. The TPS simply reads the position of the TB and sends this data to the cars computer. The above instructions are for setting the base idle on the vehicle. Once the base idle is set correctly, the car adjusts the idle from there based on engine load and ambient conditions.
look under the hood for the sticker that says the idle is not adjustable. then mess with the screw. i moved the screw on my car to get better throttle response, the idle DID NOT change one bit.
The idle is very much adjustable....the base idle. I think we are confusing the base idle with the internal idle control which is run by the computer. The idle screw is right on the TB. If you move the set screw in or out, the base idle will change. However, the car will try to compensate and run the car at the preset computer setting. If the base idle is too low, for example, the idle will tend to "hunt". It will jump around trying to find the correct sweet spot. A low base idle setting can cause for a rough or jumpy idle. A high base idle setting will definately result in a higher idle....if you turn it up enough.
I believe Ford does not want folks messing with the set screws because it really can mess things up and then is hard to correct. I think most of the after market TB come with inspections that say that the set screws are "set" at the factory and should not be adjusted. However, my experience is that when installing a new TB, they often require the base idle to be corrected anyway.
I believe that we really are both correct and I apologize if I seemed liked I jumped on you. Giving advice to the wrong person for moving the set screw can create some real problems. But, you will see that a lot of folks complain about their idle after installing a new TB...this is because the base idle needs a little adjustment.