Warm-up rpms

[CraigSmith]

The dealer didn't recommend idle-up as idling was supposed to be bed, but the higher the idle speed the better it should be I would think. The manual says it will increase idle speed after a couple minutes of idling to increase combustion temperatures, or when it's really cold. I haven't experienced the former yet, and the latter only a couple times.



Apparently the latest programming favors a regular idle speed though. So what are your thoughts?



What about driving -- would using tow/haul or locking out 4th or 5th gear improve warm-up? Or should I just let it run its course? Sometimes it will be loafing along at 1100 rpm and it's not warmed up yet.

 

[HBarlow]

Software updates have improved the regeneration process. There are at least two regeneration modes that occur as directed by the ECM . . . a passive regen and an active regen.

Have the fast idle program activated by your dealer and use it if you choose. I do. All of them since 2005 or so have factory programmed idle up feature for low ambient temperatures.

The emissions control equipment and regeneration process will take care of itself out of sight if you just drive the truck. Some of the warnings such as never allow it to idle and drive it like you stole it are exaggerated. It is a drive cycle of short daily commutes that never allow the engine to reach and maintain normal operating temperatures and no highway operation, no towing, and no hauling that will probably cause you problems.

I don't allow mine to shift into 6th gear until engine temp is rising off the peg. It is probably completely acceptable to let the ECM and automaic transmission do what it is programmed to do but I don't like to see it run in top OD at very low rpm when cold.

 

[Hoefler]

I have used the idle up feature not only to help warm up in the cold, I have used to get the A/C going in the summer while hooking up one of my trailers.

 

[CraigSmith]

I have used the idle up feature not only to help warm up in the cold, I have used to get the A/C going in the summer while hooking up one of my trailers.

That's a good idea!



Thanks again for all your advice.

 

[pcarlson]

I the TDR magazine an issue or two ago Robert wrote about this subject. To paraphrase it is not necessary to idle up via cruise control with the latest flash as it has an idle up feature. After 5 minutes of idling it will cycle idle rpm up and down to control soot and turns off when driven over 20 mph or turning the truck off. I believe that hitting the high idle on the cruise will disable this feature. This also has nothing to do with the high idle for low temperatures that the ECM already controls.

 

[CraigSmith]

Good to know, thanks. I just wonder though that it seems there are a lot of compromises, and is it bad to idle up a little more? Sometimes the behavior of my truck doesn't seem very consistent.