Tuning Idle on 1993 Ford Mustang

Hi All,

New to tuning. I have a 1993 Ford Mustang with a 306cu/in motor, aluminum heads, and a mild E303 cam, 76mm MAF (stock is 55mm), 70mm Throttle body (stock is 65mm). I interface with the factory ecu using a Moates QuarterHorse and Binary Editor software. Once the car is warmed up (180F) I can dial in the idle fuel & air, but if I turn the car off and then restart the car it seems to search (surges up and down) for the idle. I've been following idle reset procedures via forums related to my ecu, but was curious if there is any best practices for properly tuning the idle. Any advice would be much appreciated.

Thanks,

Glenn

I'm not familiar with that particular platform so I can't be too specific unfortunately. My first point would be to ensure that you've correctly calibrated the PCM to suit the larger MAF housing. All of the load calculations are based off the measured airflow, so if this is wrong then everything will be off and it's going to be all but impossible to get a good result.

My guess based on your description is that you are going to need to make some adjustments to the base idle airflow tables. If the base idle airflow target is too low, it's likely the engine may surge at startup while the ISC system tries to achieve a stable idle. Of course this assumes that your air fuel ratio on a restart is in the ball park first.

Thanks Andre. I'll check into the base idle airflow. I believe I've correctly calibrated the MAF function for the larger MAF. At a warm stable idle and an AFR target of 14.64 I'm seeing between 1.03 and 0.98 lambda.

I haven't had the opportunity to play with the Moates software but when using the factory ecm, I've had good luck following the basic idle reset procedure. You may have already gone through these steps but if not, here's the procedure.

http://sbftech.com/index.php/topic,1031.0.html

I wouldn't think your IAC is defective, if your trouble is only after a warm engine restart, so this might be a good place to start. The trouble is during a warm restart right?

Thanks for the info Rick. I've tried something very similar, but this article has a few distinctions that I haven't tried yet. Yes, it's just during a warm restart. I'm working my way thru the tables, functions, and scalars that the QH exposes for idle. I'll get there just a huge learning curve.

No problem, I'd be interested in hearing the solution, when you figure it out.