Problems with Ford PWM IAC

[terkaa]

Hi,

I am trying to add PWM idle control valve to my system. I have MS-II V3.0 and I have done the steps on assembly manual for PWM idle control(TIP 120 in place of Q4 etc.) Problem is that when IAC is connected and power is turned on IAC starts to tick for about 10 seconds then it stops and Coolant temp gauge and Intake temp gauge go to max(330 F). If I take connector off from IAC valve everything is ok. I have measured that IAC coil has 8.0 OHM resistance and it draws 2.1 Amps current at 13.8Volts. Also I have checked that there is no internal diode in IAC.What could be wrong? I have double checked everything.


Tero

[Matt Cramer]

Does this problem only happen on the car, or can you duplicate the problem on a Stimulator?

[terkaa]

Hi

Stim works ok. Led brightness changes with PWM frequency.


Tero

[Matt Cramer]

Is there a chance anything is shorted to VREF?

[terkaa]

I have to double check this I used original CFI DC motor idle controller wiring to connect PWM idle valve. It might be possible. But it is strange that I can leave all wiring on and everything works ok until plugging connector into IAC solenoid. And TPS gauge on megatune does work ok even when CLT and IAT jump to over 300 F


Tero

[Matt Cramer]

I have to double check this I used original CFI DC motor idle controller wiring to connect PWM idle valve.

The DC idle control motors won't work with PWM output. I didn't expect the sort of problem you're experiencing, but I also don't see anything good coming from wiring a DC idle motor to the MegaSquirt.

[terkaa]

Hi,

You misunderstood me. I used its wiring not the motor itself. Motor was replaced with PWM IAC from 1986 F150 pickup.


Tero

[terkaa]

I checked the wiring and it is ok no leak to vref or anything else. I noticed one thing more:

If I disable idle control and use Fidle as spare output. Then on stim I get 11.80 V when output is activated.(measured between +12VDC and Fidle)
On vehicle I get 7.4V even when i cut the Fidle wire completely from vehicle harness. Also I measure Vref with IAC connector unplugged and it was 4.94V after connecting connector it was still 4.94 Volts.

[terkaa]

Now I have found the problem it is:

12' MegaSquirt Wiring Harness has been wired incorrectly F-idle goes to pin 31 instead of pin 30 and IAC2B goes to 30. I connected MAF sensor to IAC2B and I am really hoping it did not get damaged...


Tero

[terkaa]

I was hoping too much MAF is dead

[Matt Cramer]

Sorry about that - I haven't seen that mismatch happen before. They are hand-assembled so it's not 100% mistake proof. Glad to hear you found it.