Engine/Transmission (1998.5 - 2002) High Idle ramp-up @ 31F?

[WTBurke]

I'm in Butte Montana today and have been traveling in the Rockies for a week.

Temperatures have been in the high 30's in Salt Lake and Idaho Falls but... this morning in Butte it's 31F.

I started my CTD at 7:20 am and noted the 31F reading.

I received my SMARTY 4 months ago and I run this mostly stock truck on SW# 3.

I recently moved my IAT into the intake air-horn (drill & Tap) about 30 days ago.

I didn't notice any change in operation of the CTD by doing this mod.



In starting the CTD this morning I was standing outside of the vehicle with cup-o-coffee in hand hence I didn't touch the brake or accelerator. She started as normal however;... . after approximately 1 minute 40 seconds (my best guess) the CTD began to ramp-up the idle to 1175 RPM !



I'm like... . wow!!! This is way cool!!!!



How can this be? I recall high-idle ramp-up in the past being down in the 20's some where... .



Has anyone experienced this at 31F?



I'm not in cold WX very often and to see this was very cool but, I just don't get it... . according to all the years of thread reading about this feature I'm at a loss to explain this?



As you can see my CTD is pretty much factory stock except for some quality enhancements.



Is this something that Marco has done with the most recent Smarty boxes?



Seriously guys... I'm really astounded to have made this observation this morning..... It IS very cool but I don't get it... . how can this be?



William

 

[Mad Bomber]

That just means it works well. Also it could be if your AIT is dirty. The 1st time it happened to my I'm like WTF It sure makes a lot of noise in going to 3 cyclinders.

 

[WTBurke]

Well... the IAT was pretty clean when I removed it from the factory location. I have an automatic trans and no exhaust brake. I cleaned the IAT before nesting it into it's new location. This new location certainly makes servicing the IAT easy but, because of the new location carbon build up will be a thing of the past.



Also... the CTD did not do the 3 cylinder drop-out in this scenario. It did ramp-up and according to all the common knowledge this high idle should not have occurred at this temperature.



Don't get me wrong... I think high idle should occur much earlier than what the factory programs into the 2nd Generation rigs but, with this condition occurring at 31F I'm just totally confused and pleased at the same time. BUT... why this occurred puzzles me?



William

 

[WestTN]

Since the IAT is there to control the grid heaters, I wonder if you will have excessive run time on the heaters or perhaps none at all if no heat is seen in the intake.

 

[Gary - K7GLD]

My IAT is clean, and still in the OEM location - and I have seen the RPM ramp-up at temps in the 30-40 degree range - nothing severe, but from the normal 750 RPM or so up to about 950 - hasn't gone above 1000 yet, nor has the 3 cylinder bit been experienced so far...

 

[SnoKing]

My IAT is clean, and still in the OEM location - and I have seen the RPM ramp-up at temps in the 30-40 degree range - nothing severe, but from the normal 750 RPM or so up to about 950 - hasn't gone above 1000 yet, nor has the 3 cylinder bit been experienced so far...

Gary, I don't think you have seen high idle, as it will ramp right to 1175-1200. Touch the brake or fuel pedal and it will go back to normal idle. If it is still cold it will ramp up again.



I have had the TSB for many years now, and this is what I have learned.



It takes a really good long cold soak of 8 or 10 hours in cold outdoor temps around 30 degrees or so, or lower, to cause it to go into high idle. Get down to 15 or so, and it will go into high idle and a few seconds later, you will mess your drawers the first time it goes into 3 cylinder idle. I have found that if I have the Bank EB on warmup and it goes into 3 cylinder, the engine dies.



To test all of this book room at the Timberlodge motel in Cle Elum, Wa in January or February, park your truck around 5pm away from the building out back with snowmobile trailer attached, do not plug into the power outlets hidden in the bushes in the little island there, and go out at seven the next morning. Cycle the grid heaters a couple times, and crank her up. Step out and talk to your buddies, and listen to it ramp up. I have been in Cle Elum when it was cold enough that I could drive across the street to fuel up the snowmobiles and it went into 3 cylinder idle for a second time. Now that is cold!



I can park the truck during the day at a snow park in mid twenties, and come back in 6 hours and it would NOT high idle, as the cold soak was not long enough.



Dealers seem to have a hard time turning this feature on. I had to go back the second winter after this feature came out, and work with the tech, showing him the second page screen that says turn on 3 cylinder idle, which actually turns on both high idle and 3 cylinder idle. So Smarty is the easiest way to get it on.



So to the guy that got it to high idle at 31 degree's, moving the IAT may have effected it, and maybe it was colder early in the morning. Remember "needs a good long cold soak!".



Chris

 

[WTBurke]

Chris,

Thanks and this morning in Butte it was 19F. She ramped-up the idle as clock work and for fun I tapped the brake. She dropped the idle down to normal and sitting there for 1 minuet she ramped back up again. So this thing knows whats going on.



BTW once she ramped up, the grid cycling stopped after two short cycles... . the high idle function must have priority over the grid cycle function.



William

 

[Mad Bomber]

I have a old AIT sensor that is missing the resistor. So my truck see's cold all the time. Even at 50* it will ramp up to cold idle.