3.9 idle speed

[stevegibbs]

Hi, can anyone offer some advise on my idle speed problem on my 3.9 disco. 1994

All the breather pipes etc checked, ignition ok, wires seem ok plugs etc etc

I think the problem may be with the throttle control valve (stepping motor) but cant work out how to test it. Motor will tick over when hot at about 700rpm but if you put any heavy electric load on ie heat, lights windows the revs will drop and stall the engine or surge the rpm then stall. And is it possible to change the idle speed in the cpu anyway as i would like it higher.

Thanks Steve

[teabag]

Between 665 to 735. You can't test a stepper motor only clean or replace.

[First_Fleet]

You can't test a stepper motor only clean or replace.

But you can check it's stepping movement with the valve removed & plugged in though.

1. Remove valve & lay on heater hoses with the plug reinserted.

2. Operate any security system lockout so the ignition will energise.

3. With arm through driver's window or getting someone else to switch it on, operate the key to the ON position & watch for movement .ie. It should drive forward on a cold engine to close off the port, if it was there.

The valve (& port) just may need a good clean with carby/throttle body cleaner & lube

**** Don't attempt to operate the valve manually & ensure the pintle tip is adjusted to a max. of 28mm (1 1/8") from the gasket sealing face to the tip, before inserting. If set too long it can be damaged as you screw it in.

It needs to be adjusted correctly by taking the tension off the spring & rotating the pintle to achieve the above dimension. Then make sure the spring end drops into the tiny notch on the pintle or it may undo again by itself.