1600+RPM Idle. Wtf?

[Serfma]

96 Cobra, 2.1KB just recently added. Long tubes, EGR deleted. Idle sits with an idle flag of "RPM Lockout" and sits at 1.4 vmaf. Using Quarterhorse + BinaryEditor for flashing. A previous tuner had me flash via TunerPro RT and it had a higher idle set for datalogging purposes (reach stabilized engine temp faster) and it almost seems like it has persisted through tunes.

I have verified I don't have a vacuum leak. I've caused a vacuum leak and idle does not raise, vmaf still sits at 1.4v.

I have replaced my idle air control valve. No changes. Unplugging changes nothing vs plugged up.

I have changed a few idle / dashpot settings in the tune, unless I missed the one that would affect idling down, none of them changed the characteristics any.

I sit in open loop for dialing in fueling but I have forced closed loop just to see: same thing.

It drives me insane because it will go up to 2000 at first (RPM adders I've noticed) then drop down after however many seconds / reaches X temp, but always to 1600.

CDAN4/LLX3

If anyone has any wisdom I'd love to hear it because I'm about to lose my mind. Lol

 

[98 svt]

When you first start it too, or only after the car seems to have warmed up after driving it for a few minutes?
An IAC restrictor plate may help. Try a good search if you haven't heard of them.

 

[Serfma]

When you first start it too, or only after the car seems to have warmed up after driving it for a few minutes?
An IAC restrictor plate may help. Try a good search if you haven't heard of them.

At all times. It will idle higher than usual, which is the typical characteristics it has: "idle high at warm or throttle blip, settle down after X seconds". Duty cycle seems to be at 17%, going to double triple check with smoke through the intake to make sure no vacuum leak.

 

[Serfma]

Ok interesting. I replaced IAC, no go. Unplugging IAC changes it nothing at all. Setting duty cycle to 5% or 99% changes nothing at all. I get 12v at the sensor pigtail but reading 0 duty cycle %. PCM damaged perhaps? Pin 83 on the ECU.

 

[Serfma]

Tapped into W/LB wire for IACV on ECU, 0% duty cycle. (red on + on connector, black on W/LB wire coming from ECU). Checking PCB and seeing nothing damaged, no schematics available it seems.

 

[Serfma]

I need to delete this thread permanently because I went through a few IAC's and they were all bad except this last one. Oops.

 

[jman37]

Was going to say, if your car does nothing with an IAC unplugged you pretty much answered your problem. Car should def die when unplugged.

 

[03cobra#694]

No, you don't want to delete this. Others will learn from it on a search.

 

[adammdennis11]

When you first start it too, or only after the car seems to have warmed up after driving it for a few minutes?
An IAC restrictor plate may help. Try a good search if you haven't heard of them.

Check this out!
Idle Air Control IAC Restrictor Plate Fit for Ford Mustang V8 V6 GT 4.6 5.0 3.8 1986 - 2004 https://a.co/d/5ffMT6f