Thread: Poor Idle When Warm

what motor do you have?

Originally Posted by marzzzzzz

Hi all and thanks for your help in advance.

sympoms:-
Engine idles surges down approx 500rm until engine stalls. this only happen once engine has been running for a while. it is not hot or over heating but when all engine bay components are heat soaked.

Has anybody had this happen to them?

cheers,

Marz.

It would help if we knew what engine you are talking about.

John

i bet it's a v8, and the problem is the stepper motor,
the stepper motor is on the rear right side of the plenum [inlet manifold with 3.9 cast into it.]
just remove the stepper motor and clean things a bit, put it back in and drive it, most times this gets it going

One thing Harry forgot to mention, DON'T touch/pull/push the pintle end when cleaning it, as you can damage it irrepairably. IE don't let inquisative hands NEAR it.(What happens if I just pull or push this thingy??)

Also, clean the throttle body around the throttle butterfly with carby cleaner, as it still has to have an air gap of .05mm even though most manuals don't say so for the hot wire EFI system.

It also helps to check the ignition timing, and advance up to 6 or 9 degrees, as these engines need it.

JC

Also, clean the throttle body around the throttle butterfly with carby cleaner, as it still has to have an air gap of .05mm even though most manuals don't say so for the hot wire EFI system.

I agree with the above cleaning procedure.

Having just gone through replacing the Vacuum Advance unit, I wonder if this gap would have a bearing on the vacuum pulled to enable the unit to advance on idle? Too much, & it wouldn't suck on it maybe?

How does one set this gap btw?

I have the same problem I think.
Well when I start my 3.9 up when its warm the revs go up to about 1200rpm and then drop (takes about 5 secs to drop) to about 800rpm or It starts and then stalls right away.
When I start it when the engine is cold it runs sweet.

Before the LR dealer in town closed I too it to them and they couldnt figure it out, they told me they couldnt get the base idle down passed 700rpm.
Im going to try the cleaning of the stepper motor and see if that helps, but Im unsure what it could be.


Cheers
Bulli

if the hot wire unit has poor connections you can get this symptom too.

Hot wire unit??

What and where is that?
Never heard of it