Ford PWM IAC problems still

[thecrew2999]

ok i dont know if im not getting this or what but the guide says use a 4001 diode on the PWM wiring for flyback purposes and i wired the diode up with the brand on the positive side and the other end to the - side, played with the settings, then put the diode just on the positive side banded end going to incoming power, then did this all backwards. each time playing with the settings.

i cant get the MS to control the PWM IAC i tried to use setting another member used for his since he was running a 5.0 mustang in the 90s generation which is the same exact IAC with no luck.

i have the settings for -40 to 160 at 80 - 1% and played with a few different combos there.

the hertz i set to 240 (tried ever combo i could think of) and the start value 160 and a few others...

no matter what i get 2500 rpm idle..

i even thought i blew the transistor before so i replaced it with another TIP120 with no luck...

what am i missing what else can i do to get this to work?
im getting to the point im gonna set the screw to keep the throttle plate open and say screw it..


any help would be great, thanks in advance

[Matt Cramer]

What happens to the idle if you unplug the IAC valve? Does it stay at 2,500, or does it drop?

[thecrew2999]

it drops and stalls...

im not saying i probley didnt have a combo 100% like i might not have got the HZ for the IAC perfect but i figured it would start to respond if you got close...

another thing is how do i find out the hertz of a certain IAC valve?

now i know i dont have any wires touching for what is it Q14 i think is the PWM driver?
i have it wired correctly basicly you swap 2 of the wires and the other goes as it should...
im just saying i know for a fact its wired correctly...

with my base tune setting it will idle along real nice if you unplug it and keep your foot at like 1-5% TPS

is there anyone who has done a ford PWM valve on something like a mustang or something around the 80's-90's? maybe i could just use their settings see where it gets me...

[thecrew2999]

heres the msq file

[Matt Cramer]

We've tested a couple stock Fords with an oscilloscope; their IAC valves seem to run at 300 Hz normally.

If you test the MS on a Stim, does the FIDLE light go completely out when you turn the CLT knob up to the max?

[thecrew2999]

no ever since day 1 when i first used the stim i always had the Fidle light stay on no matter what the condition..

you asked that before when i was thinking it was because i didnt put the diode inline or settings might have been off is what i thought the reason my IAC didnt work..

[Matt Cramer]

It sounds like the circuit you have controlling it may be shorted out then.

[thecrew2999]

i know we all make mistakes so i read over the manual again and i think i might have found what it is...

on the PWM you put the 4001 diode on the + side going to power the PWM and the other end of the diode goes to PIN 30 for the wiring harness the relay for Fidle solenoid..

so all i do it splice the 4001 diode into the + side and put the other end of the diode on the wiring harness for MS itself... i dont cut any wires....



i put the MS PIN 30 for the Fidle into the negative side of the PWM and its grounded out threw the MS not the factory setup.
im assuming thats where i went wrong, i dont cut the negative side of the PWM?

[thecrew2999]

is there anyone who has experience with the ford PWM iac who can tell me how to set this up?

ive tried every single combo i could and the freaking thing still dont work...

i ended up turning out the idle screw so the car would idle...
i got no response from the IAC at all to hint im going in the right direction...

[thecrew2999]

It sounds like the circuit you have controlling it may be shorted out then.

thank you so much for the help... i finally got it figured out and it was indeed user error..

when i burnt out the first transistor driver for the PWM i removed it and replaced it when i did that i tore the mica insulator some and the new driver was grounding out on the heatsink area and it caused it to stay open hence the Fidle light staying on the whole time...
i fixed the problem and now the Fidle light comes on and goes off with the temp...