Idle at start up

[Brahmajoe]

When I start the Jeep even after parked for a couple hours rpm starts at 1000 and stays there for a minute or two, then drops to 500. I had the z60 update performed. Prior to that the rpm’s would start around 1000 but definitely not stay as long and just drop to 500 ish. Just seeing if upon start up anybody’s here stays around 1000 for a little bit.

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[TigerInFL]

Yep

 

[ShadowsPapa]

Depends on the ambient air temperature - or what the temperature it thinks it is, is.
Once it pulls in the air and can get some measurements, it may settle - or not, depending on how cold it is.
Mine stays up at 1400 for a bit when it's 20 degrees.

 

[Lunentucker]

Depends on the ambient air temperature - or what the temperature it thinks it is, is.
Once it pulls in the air and can get some measurements, it may settle - or not, depending on how cold it is.
Mine stays up at 1400 for a bit when it's 20 degrees.

It's almost like they have sensors on them to figure that stuff out.

 

[ShadowsPapa]

It's almost like they have sensors on them to figure that stuff out.

Dang, what will they come up with next???

 

[Flyboy2109]

Yes, and it is very irritating in a manual shift!

 

[ShadowsPapa]

Yes, and it is very irritating in a manual shift!

Why? Is this your first manual transmission?

I grew up driving in the 1970s with chokes and fast idles that hung in at 1500 RPM or so, every car or truck I had for years was a stick.
Back then it may take a few minutes to get back down to 600-700 RPM warm curb idle. All the while the choke is coming off, dropping off that fast idle cam, you had speeds HIGHER than these things do even when cold.
I guess I don't see the irritation when it's actually far far better than cars we grew up with that idled faster for longer.
Heck, even the 1994 4.0 in my car has a higher idle when cold and it's a T5 transmission.
This ain't new or different.

 

[Flyboy2109]

Why? Is this your first manual transmission?

I grew up driving in the 1970s with chokes and fast idles that hung in at 1500 RPM or so, every car or truck I had for years was a stick.
Back then it may take a few minutes to get back down to 600-700 RPM warm curb idle. All the while the choke is coming off, dropping off that fast idle cam, you had speeds HIGHER than these things do even when cold.
I guess I don't see the irritation when it's actually far far better than cars we grew up with that idled faster for longer.
Heck, even the 1994 4.0 in my car has a higher idle when cold and it's a T5 transmission.
This ain't new or different.

Hey Bill, You aren't the only one that ever drove a stick! Been doin' it since my 65 Barracuda with a three on the tree. How about you? Think some about your comments. 700 rpm with a carb on the high idle cam is different than 1000 rpm with EFI.

 

[jimcasada]

A manual transmission should idle a little higher than an automatic. I think the EPA wants all new vehicles to idle as slow as possible. Mine barely idles at 600RPM, usually after a couple minutes warming up. That seems too low to me. You can easily kill it, if not paying attention to the tach. The clutch also has a funny feel to it, and it's hard to tell with your foot when it's starting to engage (like on most manual transmission vehicles). Making matters worse, I can hardly hear how fast the engine running with this stock exhaust system. I'm going to try to set my idle at about 800RPM, once I can figure this Jscan stuff out.

 

[Brahmajoe]

Mine never really idled over 600 for that long. I like it because I feel it gets the oil moving to the lifters quicker. This has been happening after my z60 update. I see some people have t had any change. I used to idle slower quicker and have more of a rough idle at start up

 

[Rainman519]

I always let mine idle until it drops to ~900RPM before driving. Just old-school thinking that it allows things to warm up, fluids to circulate, and sensors to get proper readings prior to take off. Maybe it's needed, maybe not, but it make me feel better.

 

[Maximus Gladius]

It's almost like they have sensors on them to figure that stuff out.

Very true but that MAF(mass air flow) sensor in the intake tube also gets coated in dirty oil vapour coming up through the PCV and if it’s never been cleaned, will result in weird idles and other idle anomalies and less MPG.

OP, have you checked and cleaned the MAF sensor? What’s your mileage at?

 

[Maximus Gladius]

Started my truck this morning. I park in a coolish garage, 12c.

Idle at 1500 then slows down to 700ish in 60 seconds.

 

[Brahmajoe]

Very true but that MAF(mass air flow) sensor in the intake tube also gets coated in dirty oil vapour coming up through the PCV and if it’s never been cleaned, will result in weird idles and other idle anomalies and less MPG.

OP, have you checked and cleaned the MAF sensor? What’s your mileage at?

I have its at 16000 miles. It still looked yellow. Wasn’t sure if I should spray some cleaner on it. This is the air temp sensor correct?

 

[jav_eee]

This is every modern day vehicle. My work truck (2020 Silverado) does the same thing. My 2004 F250 6.0 does the same thing. They do that.

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