High idle on cold start

[Flatus]

Does anyone else notice a rough idle at cold start up during the high idle? Mine runs rough and sounds like misfiring is happening during the initial cold start high idle. Seems to run fine any other time. My wife has a 2024 Expedition and hers seems to run and sound smoother than mine at initial cold start. They both have 3.5 EB.

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[jfalat]

Does anyone else notice a rough idle at cold start up during the high idle? Mine runs rough and sounds like misfiring is happening during the initial cold start high idle. Seems to run fine any other time. My wife has a 2024 Expedition and hers seems to run and sound smoother than mine at initial cold start. They both have 3.5 EB.

My 3.5 is ruff and seems to have a little miss fire on warm up…but I feel all 3 truck I’ve had with 3.5 did the same thing on warm up

 

[Dave1965]

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.

 

[Dave1965]

Regarding, the second point, turbo's do NOT make any heat on the exhaust manifold. They will heat the intake air through compression though , hence the need for the intercooler.
Here's a fix for the manifold problem:Flying Wrenches Ecoboost Exhaust Manifold Fix

 

[TheGoatman]

Regarding, the second point, turbo's do NOT make any heat on the exhaust manifold. They will heat the intake air through compression though , hence the need for the intercooler.
Here's a fix for the manifold problem:Flying Wrenches Ecoboost Exhaust Manifold Fix

This seems correct.

More time during cold start to get the cat warm as the turbo takes some of that heat for itself, but nice during a long high load condition reducing COT powerloss

 

[NVRANUF]

Regarding, the second point, turbo's do NOT make any heat on the exhaust manifold.

I’ll agree in part that the turbos don’t generate heat on their own—the heat comes from the exhaust stream—but the turbo does introduce restriction at the turbine inlet. That restriction elevates exhaust gas pressure and temperature right at the manifold-to-turbo junction. There’s a reason the manifold, turbine housing, and even the turbine itself can glow under heavy load: the exhaust energy is packed into a very small area as it hits the turbine blades.

This is why I prefer to let my truck come off high idle before driving. That short, no-load warmup lets some gradual heat soak occur in the manifold, turbine housing, and associated metal before the system sees real load. If you jump in and drive immediately—especially if you get into boost—you’re forcing a much sharper temperature spike into cold metal that hasn’t expanded yet.

That sudden thermal shock is exactly what I’m trying to avoid.

On the intake side, the intercooler is there because of the heat generated in and around the turbo. The intake air is compressed by the turbo and routed right through a housing that’s sitting next to exhaust gases that can be 900–1,400°F under load. That makes the intake charge significantly hotter and less dense, which reduces how much fuel you can safely add, which in turn reduces power. The intercooler drops those temps back down so the air is denser, so more fuel can be added to it, and the engine can make efficient power.

All of this comes back to the same point: the more load you put on a turbo system before the metal has even started to expand and stabilize, the harsher the thermal conditions are at the manifold-to-turbo interface. I believe a short, moderate warm-up simply reduces that stress.

 

[Nassau]

I have noticed the high idle on my Powerboost when it’s cold. But I don’t wait to drive. Maybe just a few seconds to get my seatbelt on and put my phone on the charger. I just don’t gun it until I have driven a few miles. IMO driving a cold engine gently while it warms up is not going to hurt anything. And, if it did damage things, then the engine must be a complete POS and we should never buy a Ford.

 

[franksfords]

you tube's fordbossme suggest letting engine idle until it settles (drops RPM's) before driving. I have been doinfg that for years anyway.

 

[Goldeneye36]

I have noticed the high idle on my Powerboost when it’s cold. But I don’t wait to drive. Maybe just a few seconds to get my seatbelt on and put my phone on the charger. I just don’t gun it until I have driven a few miles. IMO driving a cold engine gently while it warms up is not going to hurt anything. And, if it did damage things, then the engine must be a complete POS and we should never buy a Ford.

Do you have Eco idle enabled? If my engine comes on while parked it will never drop below 1200 RPMs due to that setting.

I haven't been too worried about the warm up with the hybrid as that would be an obvious engineering concern that Ford would have been completely inept to not consider. That being said, our new house has 95% of my drives putting me on the highway in less than 5 mins from my driveway so I've been keeping a closer eye on the temps (mainly the transmission) when getting ready to merge, especially as it gets colder. So far the truck hasn't complained at all.

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