Hi guys
I have a ef xr6 manual
The engine doesnt like to idle.
The idle speed Seems to drop every couple of days. Ive traced it back to the ecu
But unfortunately im unable to find a ecu.
Is it possible to use a auto ecu and bridge some wires?
The ecu code is 4TAB.
Any help would b great?

i have an auto ecu in my manual el xr6, pretty sure it used the manual loom. no issues what so ever

More information would be handy, what tests did you do to come to he conclusion it is the ecu.

I checked the wave pattern coming from the ecu to the idle solenoid and there is nothing coming out.
If i change it for a different ecu it will idle but run rough. And there is a wave signal from the ecu to
The idle solenoid. The other wire goes through the harness to the injectors so its getting nothing from there either.
Ive ordered a j3 chip from ti performance to piggy back off another ecu that works ok but its not the right one for car, so fingers crossed when that comes in that it works

Battery voltage is fed to the idle speed control motor from the main control relay. Then through the idle speed control motor to ground inside the ecu on pin 83, It dos not go the other way, so if you have no battery voltage from the main control relay splice it aint going to work.

I was under the impression the idle speed control motor gets power from the ecu? Which main control relay are you talking about? Where is it located?

Your main control relay, when you turn the key on you should have battery voltage on fuel pump relay, broadband manifold solenoid, idle speed control motor, injectors, canister purge ect. If you pull the plug off the idle speed control motor with the key on you should have battery voltage on one pin. This is how the idle speed control motor works, when you turn the key on battery voltage will flow from the main control relay through the idle speed control motor to ground inside the ecu for a split second then open circuit. When you turn the key to start the ecu will provide a full ground or about 1 amp of current through the windings of the valve and this in turn will open the plunger to its maximum position or air bypass. When the engine starts the ecu will supply a constant 160htz and will duty cycle the ground depending on engine loads and temp. If you were using a cro the wave form would look like a shark fin, scope meter a square wave, if you were using frequency you will only see the 160 htz that is constant, duty cycle meter around 40% if the engine was idling around 700 rpm.

With a test ecu i have 160hz running, with the original i have nothing. No signal at all.
Ive got power everywhere it needs to be but the solenoid to keep it idling.
The test ecu will run the car just not very well. Im quite confident its a ecu fault

I've seen similar in the past on an NL fairlane with no ISC control. With the original ECU fitted, cycle A/C on and off - you should get an immediate rev increase with A/C on. Cycling the steering should give you a slight rev increase, not as much as A/C. Increase revs to 1500-2000, take your foot off - if they drop very quickly, you have no ISC control.
With working ISC control, if you pull the ISC plug at idle, the engine should stall.

Theres no increase in rpm. It just loads up more. Ive run out of adjustment on the idle screw but i shouldn't have to adjust that anyway. If i dosconnect the battery and reset the idle its ok for a few days again

Any wonder ISC is not working, you have screwed the base idle screw out to it's limit taking the throttle position signal voltage to probably 1.5 volts or more. The ecu is not going to try to keep the idle steady, it thinks the throttle is open. You must have a problem some where, a good engine would be reving at 2000 rpm with that much throttle opening. Take the car to someone with a scan tool and scan all the operating pids. When I first started doing fuel injection thirty years ago it was a nightmare, checking voltage drops on the whole system took ages, now sit in the drivers seat and look at every operating parameter on the engine, then pull the scope out when you find something not right.

Even with idle screw adjusted properly it wont idle. .75mm from memory between the stop and screw. Disconnect the isc and it should idle around 500-550rpm. Nada. Starts and stops. Still no signal from the ecu. Reset the ecu, nothing changes. Diff ecu and i had to wind the screw out to idle at 1000 but its not the right one.

It's extremely common for EF ECUs to blow the idle control output.

As stated above,very common problem for idle circuit in EF ecu to burn out/stop working. The most common cause is a blown capacitor(remember these will be the old cardboard capacitors,not the metal ones of today) in the idle circuit itself.Take the cover off the ecu,and look for a capacitor that is bulging on top.These can be repaired...An EFI specialist may be able to point you in the right direction...or you can use any Ef ecu and a J3 chip with the EF XR6 manual tune on it.