A9L2 idle issue on Ford 400

[Motozoic]

It's been years since I've looked at datalogs from the Ford 400 in my '79 Bronco, but I noticed that the idle was higher than normal and want to lower it to stock levels, which would be around 550-600 RPM. What I appear to have going on is that the ISC control is in lockout mode and unable to control the RPM via ISC at all. I am not using mechanical idle control and would like to continue to use the stock control. What's the 1st thing to do in making this adjustment? Datalog and tune attached.

A9L2_Bronco400NA_lowerIdleSpeed.BIN

Bin file

(56 KiB) Downloaded 292 times

A9L2_Bronco400NA_lowerIdleSpeed 2021_Feb_27_12-16-55.7z

Datalog from cold to hot

(741.32 KiB) Downloaded 286 times

Note that the engine has a 351W EFI lower adapted to it that is running a '93 Mustang Cobra upper, 24# injectors, 65mm TB, either 70mm Cobra or 90mm LMAF, long tube headers, mild flat tappet hydraulic cam, and EDIS8

[decipha]

you have your idle airmass set to 1.029 yet ithbma set higher so your telling the ecu that more air is flowing through the tb than what it needs to idle

your a9l2 file is severely outdated and I'd recommend upgrading to tunerpro as its far superior than BE with my gufx strategy

[Motozoic]

Thanks, Mike! I've read through your instructions on idle tune many times, but not really sure how to go about doing this. At some point I had logged this combination and dialed the airmass calculations by averaging them at numerous RPMs around idle. What function/table are you looking at when you mention my idle airmass? I see... the neutral idle air @ 552 would be around 1.029 lbm/min...

Any suggestions how how to upgrade to the latest A9L2? Yes, I've got BE going there with a TwEECer RT right now. I've got a licensed copy of TunerPro RT as well as that's what I've been using for Buell tuning.

[decipha]

submit a vehicle info sheet and ill post a startup tune for you

http://www.efidynotuning.com/info.php

[Motozoic]

I will do that. When I originally datalogged my neutral idle airflow I was running a 70mm MAF from a '93 Cobra. I'm now running a 90mm LMAF and this appears to have altered the neutral idle airflow readings. I noticed that I'm unable to get my engine to idle below 600 RPM - with the timing locked at 10 BTDC and the TB set screw backed out all the way, I cannot get the engine to stall. Is this normal or is this indicative of a problem like a vacuum leak or something? The engine passes emissions with flying colors, with CO readings around 0.0 and HC readings that are a fraction of the idle standard for the year (1979).

[decipha]

if the isc is unplugged then that means you either have an air leak. Could be as simple as air leaking past the throttle body blade.