idle up circuit/diode

[45aken]

just finishing up wiring the 4age, and my auto elec mate wants to know if you need the idle up circuit or diode (whatever it is) to be wired up to run the car.

so my questions are;

do you need it??
advantages of wiring up the circuit??
disadvantages??
how do you wire it up??

thanks

[45aken]

forgot

engine is 4age, smallport bottom, bigport top, MAP sensored.

[AndyTTR]

The idle up circuit (toyota calls it electric load sensing) is usually connected to your rear window demister switch / headlight switch / thermofan switch / all of the above. When the ECU detects that one of these circuits is switched on it bumps up the idle so the alternator doesn't struggle under the load these systems put on it while it's running at low RPM.

The diodes are there to stop the current flowing backward (so that your headlights dont switch on with the demister through this circuit).

The idle up it isn't essential for the engine to run. If the car the engine is in at the moment was originally EFI there is proabably already an output from your dashboard loom that's ready to be hooked up to the ECU. I dont have the idle-up this hooked up on my car as it doesn't seem to need it - its probably not doing my alternator any favours though.

Hope this helps.

[roadsailing]

my smallport has no cold start or idle up stuff at all, it starts first go every time, idles at 500 RPM until it warms up (few minutes) then idles at 1000 RPM.

might be a different story in winter, but i've been through some cold days before without issues.

you can hear the idle change when the thermofan switches on, but it will happilt idle at night with headights, stereo, demist etc all on.

[45aken]

yeah i decided not to run it,
im not running stuff like air con etc, so it should be all good.