Ima dipsh!t ...... this is what I meant to post 2011 Mustang Idle Surging / Stability / Stalling Issues? Look in here! - MustangForums.com 2011 Mustang Idle Surging / Stability / Stalling Issues? Look in here!
Many people have been complaining about idle issues with a custom tune, and also even on a stock tune when they first return it to stock. There is a simple answer to this, and luckily... a simple fix!
First, the reason that this happens - your PCM calibration controls the idle, and memorizes certain driving conditions and mechanical conditions. This way it knows exactly what your car needs (air requirements, etc.) to idle properly. This is stored in the PCM, so any power interruption (battery disconnected, new batter, OR ANY
PCM REFLASH INCLUDING CUSTOM TUNES
) will result in a loss of these memorized requirements. Once the car has power to the PCM again or a fresh reflash, it MUST relearn these values or idle quality will be affected. Do the following procedure to fix it (from a cold start!)
Here is the Ford owners manual text:
Because your vehicle's engine is electronically controlled by a computer, some control conditions are maintained by power from the battery. When the battery is disconnected or a new battery is installed, the engine must relearn its idle and fuel trim strategy for optimum driveability and performance. To begin this process:
1.) With the vehicle at a complete stop, set the parking brake.
2.) Put the gearshift in P (Park) (automatic transmission) or the neutral position (manual transmission), turn of all accessories and start the engine.
3.) Run the engine until it reaches normal operating temperature.
4.) Allow the engine to idle for atleast one minute. *AM note: one minute AFTER you get to peak temperature - probably about 5 minutes total from cold start.
5.) Turn the A/C on and allow the engine to idle for at least one minute.
6.) Drive the vehicle to complete the relearning process.
• The vehicle may need to be driven 10 miles (16km) or more to relearn the idle and fuel trim strategy. • If you do not allow the engine to relearn its idle trim, the idle quality of your vehicle may be adversely affected until the idle trim is eventually relearned.