To Idle or Not To Idle...

[BeepBeepInMyJeepJeep]

It's getting colder and colder here in Michigan. There are a lot of conflicting thoughts on whether or not to let your car warm up before driving it. Just wondering what the JeepKJ community thinks about this.

When I cold start my KJ, the RPMs are at an even 1000. Once it's been idling for 4-5 minutes, it drops to just above 500 RPM.

Is it "bad" to drive your Jeep cold? Should I let it idle for a few minutes before driving, or is this a waste of gas?

 

[renegade 04]

With new engines like what our libbys have you do not need to warm them up before driving because the engine is designed that way.

 

[Hedsic]

It's fine to drive it cold with newer engines. Most people idle it just to warm it up a little before driving for the heater more than anything.

Below is why it idles higher when it's cold.

When it's cold, combustion requires much more fuel in the ratio because it does not sufficiently vaporize from liquid gasoline into a gaseous form (liquid gasoline, for the sake of this discussion, does not burn). The problem is, too much fuel through the engine at a low speed bogs down the engine as the unburned liquid fuel will kill the spark and cause it to stall. The RPMs are bumped up to push this fuel out more quickly until a more desirable temperature is attained. Once warm enough, the fuel vaporizes as it should, the computer dials back the fuel mixture.

 

[wheeee32]

If you want to, you can go as far as getting a block heater installed so you don't have to worry about your Jeep taking just a bit longer to heat up. Woot! 1000th post!

 

[cplchris]

I always allow the jeep to idle for at least 3 or 4 minutes. yea new engines may be designed to run better/safer at colder temps. but the laws of physics, fluid dynamics, and thermo dynamics have not changed much in recent years, (at least not that I am aware of).

coolant temperature isn't why I let it warm up, I like to let my oil get somewhat up to temp before I drive anywhere.

a block heater is a good idea, IIRC someone on here installed one on their own. not sure how involved the install is.

 

[dude1116]

I don't fully warm my Jeep all the time...but I do NOT romp on the gas until that needle is straight up.

 

[CzarKJ]

My block heater is wonderful. When we had temps dip (plummet) below 0 last winter I never had a hard start and could drive right off without any weird cold noises

 

[CalcityRenegade]

I use my block heater and when its cold out I let it idle for 10 minutes if possible but that's just the way I have always done it, Heck I let my jeep idle 5 minutes in the middle of summer, My Sierra HD (Gas) I left idle for 15-20 minutes in the winter and drive the vehicles easy for the first couple block until up the temp.

 

[Cardhu]

Idle it and change your oil in the spring. Even with my block heater when it hits below -20c my jeep is not happy if i just take off. Its already dealing with frozen ATF fluid and square tires and requires more revs to get moving.

The more obvious reason is without idling to warm up the engine the defrost isn't going to work and your going nowhere if you can't see.

 

[LibertyTC]

If it is only a few degrees below zero, I warm the Jeep until it hits 150F on the scan gauge, then drive easy until it is fully warm.
Now if it is -20 that is a different story, I use the block heater wherever possible for 4 hours or then allow jeep to fully warm up before driving off.
The jeep is very sluggish when it is really cold initially as I have the thicker lube in rear diff.
I also go slow for a while if I have to use 4x4 mode cause the cases take a while to warm up too.

 

[CzarKJ]

If it is only a few degrees below zero, I warm the Jeep until it hits 150F on the scan gauge, then drive easy until it is fully warm.
Now if it is -20 that is a different story, I use the block heater wherever possible for 4 hours or then allow jeep to fully warm up before driving off.
The jeep is very sluggish when it is really cold initially as I have the thicker lube in rear diff.
I also go slow for a while if I have to use 4x4 mode cause the cases take a while to warm up too.

I noticed that in the rear diff as well. I usually just leave my jeep plugged in overnight on the cold nights.

 

[Jo6pak]

When it's cold enough to matter (-0 F) I let the Jeep warm up...more for my sake than the engine:icon_lol:

 

[HoosierJeeper]

I let mine warm up for a few minutes even with the block heater...it's plugged in if it's below 15 or so. May as well use it since I got it.