Parked the truck outside just to test the cold start routine. ok, cool, my 02 was re-flashed with that fancy idle speed ramp up thingie, so I expected something similar on my 04 and wasn't disapointed. she ran at normal idle speed and then slowly climbed up to 1,000 or so and stayed there. Since I wasn't about to wait for the engine to warm under those conditions, I drove off to work with the idle speed returning to normal of course. outside temp was 19 degrees.

When I arrived at work, I put her into neutral, engaged the parking brake, and began to do some work on my laptop. By this time the engine was fully warm (after the 15 mile drive) and the cab was toasty warm. outside temp now about 25 showing on the overhead.

I worked for about a minute or 2 and then to my astonishment she started to ramp up the idle speed to 1,000! I discovered that touching the brake pedal shut that behavior down.

huh. anyone else see this?

 

Yep. Working as designed. As in another thread it will even ramp up with an exhaust brake on.(activated)

 

That is exactly how mine works also. It has to do with the ambient temp being below freezing. It will idle at normal speed for two minutes then ramp up to 1000 rpm.

Brian

 

Good idea but I think there is 3 different criteria that must be met for the rpm to ramp up. One I know is intake temp. I would think another is coolant temp. I can't remember what the 3rd one is. Sounds like a good project for you Jack. I'll buy one!! ;D

 

Which temp sensor does it use for "ambient" temp?
The one connected to the overhead computer, or the Intake Air Temp sensor?

Could it be as simple as putting the sensor in a cup of ice?


phox

 

I would think that it would be the one in the intake stream. Underhood temps (which the console readout uses) would be different than the air entering the intake (through the fender and grill area) It might even use both. I'd need an electrical schematic to see.

 

Really intrested in seing my truck do this, but at 75 out side I don't think it will ;D. Guess I will have to keep wearing my shorts an t-shirts till some one send some cold air my way. Till then I guess I will just have to keep using the stick to Idle the truck up. Tough Life but some one has to live in the South.

 

Most mornings in the upper teens without plugging in and parked outside mine ramps up to 1100-1200 RPM rather smoothly. But two mornings ago when it was in the low teens the moment it fired it went straight to 1200 RPM.

It did another weird thing too. It kept varying the RPM rather quickly between 1000-1250 or so. I think it's programmed to do that to load the cylinders a bit more or something. As soon as I tapped the brake it went straight to a normal smooth idle.

Vaughn

 

Mine too did that once Vaughn. It was parked at the airport, not plugged in and had sat there for a few days in -10C temps. It started and went right to 1000 rpm and stayed til I tapped the brake. ???Some sort of glitch I suppose.

Brian

 

We have been getting down below zero and in the single digits this week. I have noticed it immediately jumps up to 1000 rpm's when it is this cold. This morning it was about 20° out and it waited about a minute or two before jumping up to 1000 rpm.

I also realize the 03 starts a lot better in the cold compared to the 01.5. The other morning it fired right up when it was -5°. Just wish the 03 high idled at 1200 rpm's like the 01.5.

John

 

[quote author=Vaughn MacKenzie link=board=17;threadid=22092;start=0#msg206863 date=1068185399]
Most mornings in the upper teens without plugging in and parked outside mine ramps up to 1100-1200 RPM rather smoothly. But two mornings ago when it was in the low teens the moment it fired it went straight to 1200 RPM.

It did another weird thing too. It kept varying the RPM rather quickly between 1000-1250 or so. I think it's programmed to do that to load the cylinders a bit more or something. As soon as I tapped the brake it went straight to a normal smooth idle.

Vaughn
[/quote]

Hmmmm....that doesn't sound like what it's SUPPOSED to do. It's SUPPOSED to ramp up to 1000 RPM's and hold there. ???

 

[quote author=Jack Thorpe link=board=17;threadid=22092;start=0#msg206938 date=1068215414]
So does anyone know which temp sensor it's using to determine when to high idle? If it's the regular sensor for the overhead computer, there might be a way to make it work whenever you want.
[/quote]

unplug the temp sensor for the readout and see if the idle ramps up. That should answer your question.