Thread: idle speed eratic

Ever since I cleaned out the PCV and the rocker covers and all the interconnecting tubes I've had the same problem, the idle is odd.

Haven't bothered sussing it yet, tho'....

GQ

Disconnecting the battery on a 14CUX (D1 or Classic Range Rover) achieves nothing as the ECU does not "learn" it just reads internal maps.

Coming to a halt the idle speed is held up via the stepper , with the ECU using a signal from the speed sensor. As you stop, the stepper drops to normal idle. sometimes it can drop to "base idle" before picking up again.
I would be looking at the "base idle" and again at the stepper and the cleanliness around the throttle blade.
It may be that some young Einstein has reset the base idle without cleaning the throttle. Ie addressed the symptoms rather than the problem.
To check the base idle , disconnect the hose to the stepper at both ends and block both ends, and electrically disconnect the stepper. The adjustment/bypass is the little allen key at the top of the throttle blade. base should be 550 to 600 RPM.
Some people say you should do some magic thing with the stepper once you have reset the base ,but in my experience it automatically compensates when you reconnect it.
Regards Philip A

I have had a similar problem with my beast. Prior to changing the battery all was well, but now it is revving when you pull up at the lights and slowly drops back to a normal idle. I have cleaned the throttle body and the maf but still does the same . I might try resetting the base idle and see what happens. Do you have to use the stepper motor? Will the car run without it?

The stepper is there to compensate for loads, eg aircon, and to rais ethe idle speed while moving to prevent clunks from the auto.
If you block both ends of the stepper,ie the pipe stub at the throttle and the pipe stub at the stepper, it will/should idle at about 550-600RPM. This is the "base/kerb" idle.
I would say you have a dirty or worn out stepper, which is slow to react.
Clean teh stepper and its mount and see if it makes a difference. If not replace the stepper.
Regards Philip A

The "magic" thing you refer to, may be the checking of the plunger length before inserting the valve body. If it's too long the you may damage it as it's screwed in. Result............. a new valve is required.

This comes from the manufacturer's instructions enclosed with a new valve.

New steppermotor and all is well thanks for the imput guys.

How much is a new stepper motor?

http://www.petroject.com.au/efi.html#13

Edited. Their P/N was 29001 Idle Air Control. JD TBI (or 1) A$118. 21/06/06




Ask for a GM 25527077 or an AC Delco 217 - 437 which is identical to LRs ETC6660. 1/2 the price as well.

I'll try & dig up the national company that I got mine from.