Idle control will not work

[lärpäke]

Hi everyone,

I have built a Ford Scorpio 1986 EEC-IV to run on MS1 v2.2 extra code with E85 and turbo. I made a harness adapter from 60pin to 37pin, so im using original wiring and sensors/actuators. Im having an issue to get the the standard Ford 2wire PWM idle air control valve to work. I have wired it correctly from MS and measured that there's a good connection. There is 2 wires coming to valve, black and brown/yellow. The black is +12v when igition is switched on (comes from the ECU main relay). Brown/Yellow wire is supposed to be ground wire, which is grounded by Megasquirt. I have replaced the Q5 with TIP122, and I have connected a diode between Base and +12v from D9 (banded side to D9), I wonder why this even has to be done, because it is the same connection as D9????

Theres plenty of things im worried, and I need some advice to get in right direction.

-If I measure voltage on the IAC connector car running, I get +12v on black, and +12v on brown/yellow, if I have the connector connected to valve. Should I add another diode to harness (There is one already in stock car harness)
-If I unplug the connecter, there's +12v on black, +3.92v on brown/yellow.

I noticed that when Fuel pump is running, I get this 3.92v on brown/yellow. I measured from ECU harness(MS unplugged) on the car side, there's a 90ohm resistance between the wire that goes in to fuel pump relay, and the wire that goes in to IAC. My friend told me that resistance might be the coil resistance of fuel relay, and it's normal. Is it that why there's the 3.92 voltage? Friend told also that it doesen't matter, because that voltage is measured off-load, in load there might be not any voltage.

What could I do to get it working, what to measure/test next? I have remade the tip122 mod like 5 times, and Im not getting it work. Once i got somehow it to pulsate the fuel pump, might I have burnt the mosfet? I assume it's not working because the settings has no effect on anything.

Here is the wiring diagram of the stock car harness, to see how the IAC is wired originally.

[Michael]

hi,

I've just completed a similar installation: 2 litre Zetec from EEC-IV to MS1. Like you I made a harness from the EEC-IV connector to the MS 37 way connector. It has a "Standard" 2 wire Ford pwm ISCV.

The first thing I note is that the diode (1N4001 or similar) should be connected from the COLLECTOR of the TIP122, not the base.

It took me a little while to understand the mod for the MS1 board, so I re-drew the diagram to make it easier for me to understand in the future. See attached picture, the lower drawing is the standard MS one and my re-drawn version is above.(note I have retained the 1 Ohm resistor in the emitter leg to protect the TIP122 - you can leave it out if you like):

ISCV Driver065 Low Res.jpg

I've also attached a copy of the spread sheet I used to work out the EEC-IV (DESK) to MS connections, you may find it useful, maybe not as not all EEC-IVs were wired the same. If is the same EEC-IV pin 21 goes to MS pin 30.

Best Wishes and Good Luck - Michael.

[Matt Cramer]

[Michael]

You need to sort out exactly how you have wired up the TIP122. If the base is tied up to +12v, under normal circumstances it would be turned hard on, however, the cause of your 3.92v at pin 30 will depend upon how you have wired the other two legs of the TIP122.

Michael

[lärpäke]

Thanks for everone, I got it solved!! Finally!

I had Collector and Emiter wired in wrong legs of tip122. I had made the same mistake multiple times

Currently I dont have the tip122 mounted on any heatshink, I just used hot-setting adhesive to mount it on the MS microcontroller. Does it really dissipate so much heat that I need to mount it on the case or the pcb?

Now I need to tune the idle right. Could I adjust the throttle closed when warm and steady idle is achieved, and set the slow idledc to 0 in settings?

[Michael]

Glad you've got it sorted!
The TIP122 does not dissipate a lot of heat mainly, I suspect, because it does not have very high duty cycle. However, heat may well build up over a period of time and in the interests of reliability, I would mount it properly on the heatsink.

I don't quite follow your last question. What I did, and most others seem to do, is to warm the engine up to normal temperature, ensuring that Warm Up Enrichment has completed. Then get a smooth idle by using the throttle stop screw and adjusting the VE table in the idle area for the best idle. Keep going back and forth until you get it how you want it. Then you can move on to the driving portions of the VE table.

Best Wishes - Michael.