1500 RPM high idle at start and then is fine

[ws11]

Has anyone with a 5.0 had an issue with a higher than normal high idle at start? Mine goes up to 1500 rpm then drops. It seems higher than normal. I just replaced the vct exhaust solenoid for a different reason. Anyone else have a similar issue or idea?

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[Dakar09]

Mine does it occasionally but drops quickly. Other times it idles a bit longer at "normal" warm up RPM. Prob nothing to worry about if it isn't throwing codes.

 

[TexasTruck]

Mine has does it since it was new like Dakar09 said. I’ve gotten in the habit of waiting for the high idle to drop. If I’m antsy and put it into gear while it’s in high idle mode, the RPM will drop to normal too.

 

[ws11]

Mine does it occasionally but drops quickly. Other times it idles a bit longer at "normal" warm up RPM. Prob nothing to worry about if it isn't throwing codes.

Ok that’s good. It drops after about a minute and doesn’t throw any codes. I didn’t put a ford oem vct, it was a Napa part, I believe made by dormon. I couldn't get one the day I had the time to work on it and it was kind of a last minute fix, I wonder if that was the issue. But it drops and runs great so I’m probably just overthinking it. Thank yall

 

[ThumperF150]

Normal. Programmed in to help warm it up. I use remote start then try to wait the 60 seconds or so it takes for the 5.0 to get to temp and idle down before I drive away.

 

[ws11]

Normal. Programmed in to help warm it up. I use remote start then try to wait the 60 seconds or so it takes for the 5.0 to get to temp and idle down before I drive away.

Thank you! I just don’t remember the idle being that high. Like I said drops and runs normal so I should stop over thinking it

 

[ThumperF150]

Thank you! I just don’t remember the idle being that high. Like I said drops and runs normal so I should stop over thinking it

My 21 Jeep JL 2.0 turbo does the same thing.

My 67 VW bug also does it mechanically and manually. Get in, hit the throttle once. That sets the start up idle based on a clock sprint in the carb which expands and contracts with temp. Turn key, engine starts and will idle high basically forever if I don’t tap the throttle again. If I tap it too soon, it will continue to idle high. That spring needs to heat up first. Hope that makes sense.

 

[Billflangjr]

Ok that’s good. It drops after about a minute and doesn’t throw any codes. I didn’t put a ford oem vct, it was a Napa part, I believe made by dormon. I couldn't get one the day I had the time to work on it and it was kind of a last minute fix, I wonder if that was the issue. But it drops and runs great so I’m probably just overthinking it. Thank yall

What's a VCT?

 

[ws11]

What's a VCT?

Valve cam timing solenoid. They refer to them as vvt, vvt and vct, essentially the same thing. Variable valve timing, valve cam timing. Some of the solenoids are specific to the cam so hence vct

 

[v8440]

Today, my truck was at about 165 or so degrees coolant temp, with oil temp about that or higher from an earlier drive. I started it to go to lunch and it idled high. Not 1500 rpm high, but obviously higher than normal hot idle. It occurred to me that a bunch of this is probably to light the cats off quickly.

 

[TexasTruck]

It occurred to me that a bunch of this is probably to light the cats off quickly.

I think you’re right…

 

[JCsTruck]

Normal, the computer retards the exhaust valve timing and raises the idle to help get the catalyst up to temperature quickly.

 

[gagliano7]

The one thing I don’t understand is my truck will be fully warmed up. I stop somewhere for 5 minutes and when I start it goes to high idle and then takes forever to drop. Never had a vehicle ever do that. Pretty annoying. On a cold start with temperatures around 40 degrees it will lower idle within a minute but hot it stays high longer. Just doesn’t make sense.

 

[v8440]

Lighting the cats back off as fast as it can.

 

[Bluegrass]

Has anyone with a 5.0 had an issue with a higher than normal high idle at start? Mine goes up to 1500 rpm then drops. It seems higher than normal. I just replaced the vct exhaust solenoid for a different reason. Anyone else have a similar issue or idea?

.
Missing is technical Infor on why high Idle occurs at cold and hot restarts.
A. All ICE engines require richer fuel when cold starting, TB is commanded to open more for extra air with the fuel.
B. Ignition Timing is advanced. A & B result in the high Idle and slowly come down as the Temperature rises.
C. Test of Six Temperature Sensors is done to be sure all are within 10%.
D. At this point a test of Cats is done for emission purposes and faster heating.
E. This test has a time limit for a 40% rise in CAT temperature from about 800* to about 1200*, then reduces back to the 800* range. The test must pass as detected by the rear OX Sensor for min. Oxygen content. If a failure is detected in either Cat, a P Code is set 420 or 430 indicating the test has failed.
F. Hot restarts are done in the same manner but accounting for the engine a partial heated condition depending on how long.
.
The Temp Sensors are:
Outside Ambient.
Cylinder Head Temp.
Map-T inside the intake manifold.
Both CAT Temps.
Transmission.

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