AMChrisRose

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:

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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.

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We're all about good customer service at AmericanMuscle. The idle quality issues sent us into panic mode. We tested our tune on over four different 2011 Mustangs overnight to try and hammer down if it was something inside our calibration just to be safe. We logged the 'idle integrator' (which is the correction for air requirements) and learned that it was unstable after reflash for a few minutes while it learned.

This is nothing new, we've logged this parameter on many vehicles that have camshafts, superchargers, etc. In 2011, the air requirements became a little bit more touchy, so this process needs to be done, while previous years responded much better. This makes perfect sense, as we've gotten complaints about multiple custom tunes from different companies, etc.

I hope this clears everything up. I've attached the Ford owners manual scan.

Nuke

Excellent info, Chris. Thank you.

Yes, this is nothing new. Many folks report idle issues after a battery disconnect and those of us familiar always tell them to put some miles on the car to allow it it relearn.

AMChrisRose

No problem!

Yeah, it's just that much more crucial for the 2011's. People always thought I was crazy when I sent them tunes and said, idle it from cold start for 10 minute without touching the throttle. Hopefully this clears that up. The only ones who understood it were those that logged ISC_Integrator so they saw that it was learning it's way down to 0.

JIM5.0

Chris, thanks so much for posting yoru findings.
This information is invaluable to us, even if it is something as mundane as replacing a batt. I for one totally appreciate you posting your findings in public among the internet forums to spread the word