Fast Idle - D4D

[MDSimpson Advanced Member Find all posts View Profile Close MDSimpson]

Help.


I need to make sure this small, seemingly insignificant problem, is not leading to, or alluding to, something larger.

Of late, last two or three weeks, I've noticed my 08 D4D Auto (almost 140k's) is idling fast when started in the mornings and also in the afternoons leaving work.
It is up around 1200-1500 RPM and only seems to drop, once in gear.


I've had it since new, and never noticed this before.

Why?

[matt150 Avid PP Poster! Find all posts View Profile Close matt150]

Dumb answers first - is the fast cold idle button turned on ?

[mjrandom Out of control poster! Find all posts View Profile Close mjrandom]

Have to ask the obvious question, no one has bumped the idle up switch? Otherwise I have no clue.

[gspy4u Senior Member Find all posts View Profile Close gspy4u]

was going to say the same thing, i use the fast idle in winter while i'm opening up the gates to warm the beastie up

may have knocked it on or kids turned it on (as mine did once)

[MDSimpson Advanced Member Find all posts View Profile Close MDSimpson]

Not sure my 2008 has a fast idle switch. Could be the cause, if I didnt know i9t was there, huh?
Where would I see this switch?

[mjrandom Out of control poster! Find all posts View Profile Close mjrandom]

You got it for sure. From memory right hand switch block.

[AJ120 Out of control poster! Find all posts View Profile Close AJ120]

You defiantly have one, look next to your right knee!

Cheers Andrew

[mjrandom Out of control poster! Find all posts View Profile Close mjrandom]

You might want to prepare for the worst... I bet the switch is feeling depressed.

[MDSimpson Advanced Member Find all posts View Profile Close MDSimpson]

Haha, Learn something everyday. Too rainy at the mo, but I'll check my right knee, see whats the go.

[mjrandom Out of control poster! Find all posts View Profile Close mjrandom]

I took this pic for other reasons but here is the little sucker. The wife and #2 son bumps it getting or out (not sure) but regarly. Only makes a difference about now.

[sellit99 Junior Member Find all posts View Profile Close sellit99]

I can't believe it!! I was wondering the same thing and yes, the button is in. Talk about feeling...doh! I love this site.

[Wardos Junior Member Find all posts View Profile Close Wardos]

Out of curiosity, would be there be any detrimental effect on having the Idle Up activated - to the engine. On one hand we could say the slightly higher idle speed will warm the engine quicker to operating temp reducing the time it is running at the colder temp and having a different (richer) fuel injection pattern as I believe is the case from threads on this forum. On the other hand, is a longer period of time to warm at a lower rpm better for the engine from a "wear and tear" perspective? Or am I talking BS and makes no difference? I do understand its purpose and here in Perth WA, the morning temps are not exactly extreme in the cold department compared to other places in world, so perhaps in Australia it is not needed.

Just wondering from a maintenance perspective what the best setting for the "Idle Up" is ie. on or off - I normally leave it off myself.

Cheers
Wardos.

[AJ120 Out of control poster! Find all posts View Profile Close AJ120]

I doubt it would make much difference one way or the other, its only 300rpm or there abouts it rises, yes it warms up in less time but the pistons go up and down and everything turns more times as well. After the engine reaches a certain temperature it goes back to normal idle anyway.

MJ posted a pic from his 150, 120 is pretty much the same but here a pic anyway taken from my rig build.



Cheers Andrew

[MDSimpson Advanced Member Find all posts View Profile Close MDSimpson]

You guys are the bomb..
It worked, and I am a twit....

Thanks All..

[Palmer Advanced Member Find all posts View Profile Close Palmer]

Superb.
My wife asked me only two days ago what that button did - and I had to admit I didn't know. Of course, my usual (helpful) suggestion of "push it and see what happens" got no response.
Now I'll at least be able to clear that one up.