High idle on cold start

[Carnious]

I’m assuming this is normal, I’m just wondering if people typically wait it out until the RPMs drop to drive? Or at the very least, would this behaviour be harmful to the vehicle?

Previously I had a GMC canyon and would do the same, but it seemed like the high idle took less time.
I was told it was due to the truck warming up the Cat converter.

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[Goldeneye36]

My understanding is that modern engines are fine without being warmed up any amount. My personal habit has always been to wait until the RPMs stabilize under 1k before I set off but my current fleet of vehicles has tossed that out the window, lol. My PB doesn't crank the engine until I'm already out of my driveway and the wife's Subaru hangs at almost 2k for a very long time before it comes down if you stay in Park.

 

[kaylub05]

I’ve noticed this too with my past 3.5 f150 and my now current 5.0 f150. I believe the high revving is just to warm up the engine to operating temp and to get oil flowing where it needs to be. I always wait till the rpm’s settle before taking off, even if I’m late somewhere. It’s also just personal preference.i also remote start my truck before I drive just to get the engine warm and the oil flowing

 

[deanfx]

I always wait a bit. Usually when the seatbelt nanny goes off, the high idle is over. I cam from a Cummins diesel, and it never high idled unless you let it sit and idle for a bit anyway. But I will say as most would with mechanical knowledge, letting anything warm up a bit is a good thing.

 

[FaaWrenchBndr]

I’m assuming this is normal, I’m just wondering if people typically wait it out until the RPMs drop to drive? Or at the very least, would this behaviour be harmful to the vehicle?

Previously I had a GMC canyon and would do the same, but it seemed like the high idle took less time.
I was told it was due to the truck warming up the Cat converter.

What model truck do you have?
High idle at start is an emissions thing. The engine is more efficient and cleaner burning at operating temp.

I do usually allow mine to stabilize before driving but usually no more than 30 seconds. Of course that is a little different in the winter when it is 10° but if it’s above 50, I rarely wait more than 30 seconds if even that. I do also avoid Fast accelerations until oil temps are up to normal

 

[jfalat]

i usually wait till it steps down to 1000 rpms before driving off.

 

[Old Hat]

30-60 seconds idling tops. Getting the engine up to operating temp without delay is best and idling doesn't facilitate that, driving does. Gently for the first few minutes.

 

[Littledemonboy]

My 5.0 takes forever to come down off high idle and I refuse to put it in gear before then because I’m worried about the transmission being made of glass.

 

[NVRANUF]

I let my truck come off high idle before driving, 100% of the time (Always happens at 121 degrees coolant temp on my 21' EB). My 13' EB F150 only comes off high idle at 151 degrees coolant temp. I do this for a few reasons:

1. These engines have variable cam timing and several timing chains that are held in place with guides backed by tensioners, all of which completely rely on oil flow and oil pressure to work properly. Warm oil flows like the engine was designed to operate, and so I don't put the engine under any load until there is some heat in the oil.
2. I've had two different Ford engines break the exhaust manifold studs, causing that annoying ticking sound (and cylinder head removal in order to fix it). On these EB engines the turbos make a lot of heat and are mounted directly to the exhaust manifolds. I don't want to take cold exhaust manifolds and quickly put a ton of heat into them by driving immediately after starting the engine, and potentially break any of the exhaust manifold studs (especially on my 13' EB which does not have the revised manifolds with the extra bolt). I prefer to warm up the exhaust manifolds more slowly to allow everything to gently expand before driving.
3. Turbo-charged engines (or supercharged) typically have slightly smaller piston diameters versus bore size to allow room for additional thermal expansion under boost. The ring end-gaps are also slightly wider for the same reason. Pistons and rings in forced induction engines see more heat while under boost and therefore need more room to grow in the cylinder bore. On cold start some forced induction engines have a little "piston slap" where the skirts tap the side of the bore until they expand from heat. Not to mention a little more ring blow-by until the ring gaps close a little under heat. Granted, on a factory-stock engine, this issue is way less than on a high-performance or race-built engine, but it still exists... and so I prefer the rings and pistons to also be warmed up a little before driving my truck under any load.
4. Fuel maps.... There is a different fuel strategy in the PCM for a cold start versus "normal" operation. The vehicle operates in "Open Loop" during cold start with a fixed fuel map that is pretty rich. Once the engine and O2 Sensors are at operating temp the PCM switches to "Closed Loop" where it relies on the actual real-time readings from the various sensors to adjust fuel maps.
5. Lastly... For those of you that are emissions conscious... Yes, the high-idle also heats up the catalytic converters so they are operating more efficiently and reducing emissions. Cold catalytic converters are doing absolutely nothing, hot cats burn emissions gasses.

 

[Old Hat]

My 5.0 takes forever to come down off high idle and I refuse to put it in gear before then because I’m worried about the transmission being made of glass.

I found putting mine in neutral prior to drive will drop the RPM's. It seems if I wait too long after start up then it won't.

 

[Littledemonboy]

Interesting. I will try this.

 

[FirstTimeFord]

The high idle at startup in the 3.5 EcoBoost is normal behavior, designed to quickly warm up the catalytic converters for optimal emissions control and to heat the engine faster.

 

[24STX5.0]

I have a quarter mile long rural driveway, so I get in and go in my Coyote. It's done high-idling by the time I coast down to the road.

My other vehicle is a BMW 335D (3.0L twin turbo diesel). It gets treated differently. No hammering on it until up to full operating temperature. Gotta be kind to the turbos. And diesels take awhile to warm up due to their thermal efficiency over gassers.

 

[PowerBoostSoCal]

I let my truck come off high idle before driving, 100% of the time (Always happens at 121 degrees coolant temp on my 21' EB). My 13' EB F150 only comes off high idle at 151 degrees coolant temp. I do this for a few reasons:

1. These engines have variable cam timing and several timing chains that are held in place with guides backed by tensioners, all of which completely rely on oil flow and oil pressure to work properly. Warm oil flows like the engine was designed to operate, and so I don't put the engine under any load until there is some heat in the oil.
2. I've had two different Ford engines break the exhaust manifold studs, causing that annoying ticking sound (and cylinder head removal in order to fix it). On these EB engines the turbos make a lot of heat and are mounted directly to the exhaust manifolds. I don't want to take cold exhaust manifolds and quickly put a ton of heat into them by driving immediately after starting the engine, and potentially break any of the exhaust manifold studs (especially on my 13' EB which does not have the revised manifolds with the extra bolt). I prefer to warm up the exhaust manifolds more slowly to allow everything to gently expand before driving.
3. Turbo-charged engines (or supercharged) typically have slightly smaller piston diameters versus bore size to allow room for additional thermal expansion under boost. The ring end-gaps are also slightly wider for the same reason. Pistons and rings in forced induction engines see more heat while under boost and therefore need more room to grow in the cylinder bore. On cold start some forced induction engines have a little "piston slap" where the skirts tap the side of the bore until they expand from heat. Not to mention a little more ring blow-by until the ring gaps close a little under heat. Granted, on a factory-stock engine, this issue is way less than on a high-performance or race-built engine, but it still exists... and so I prefer the rings and pistons to also be warmed up a little before driving my truck under any load.
4. Fuel maps.... There is a different fuel strategy in the PCM for a cold start versus "normal" operation. The vehicle operates in "Open Loop" during cold start with a fixed fuel map that is pretty rich. Once the engine and O2 Sensors are at operating temp the PCM switches to "Closed Loop" where it relies on the actual real-time readings from the various sensors to adjust fuel maps.
5. Lastly... For those of you that are emissions conscious... Yes, the high-idle also heats up the catalytic converters so they are operating more efficiently and reducing emissions. Cold catalytic converters are doing absolutely nothing, hot cats burn emissions gasses.

Not sure of all your details - but agree with your assessment, let it all warm up before putting any load on the engine/transmission - as a former BMW owner, the mechanic who did the engine "tour" at delivery basically stated. You have several individual elements, some of different types (metal, plastic, etc.) that are designed to work well together at temperature - that being said, they tend to NOT work very well until that time. I thought that was really great advice.

 

[ezndo]

2024 5.0L Coyote…..as others have stated, the high idle seems to take forever to settle out. But I have noticed a loud “chirp” when I shift into R after letting the idle settle. Only happens with the first start of the day and not thereafter…anyone else?

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