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2017 Duramax L5P base idle

jaws3
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jaws3 Enthusiast

jaws3

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After the recent recall for Emission System upgrade to comply with gov standards (done 2 weeks ago) the base idle speed has increased to over 800rpm. Used to be just above 500rpm. Dealer says the higher base idle speed is "with limits". I don't agree. Talked to 2 drivers of similar trucks today and both said there base idle speed is just above 500rpm. These are company trucks so they don't know if recall upgrade was performed on the trucks they are driving. The exact scenario is that when I start the engine, idle is normal at just over 500rpm. It stays normal when shifting into DRIVE. Then start driving and at the very first stop 700m from my house, it base idle is over 800rpm. It stays like that until I shut down the engine and it is back to 500rpm when I start the engine again after work. But only until the first stop when it stays above 800rpm. This has been going on for the past 2 weeks (during which I also did a 1200km highway trip). I cannot find a reference to base idle speed on this engine. Is 800rpm considered normal? If it is my "new normal" I'll be selling the truck as it is driving my crazy with the added noise sounding like a jet engine at startup.

Edited by jaws3
spelling
2018GMC Senior Enthusiast

2018GMC

Posted
Posted

Go to a different dealer.
 

Example:

 

We had oil pressure gauge on lml suddenly read 120 psi anytime above idle. 

 

GMC dealer said there was no max spec for oil pressure just minimum. I suggested they change sending unit as everything was fine the first few years. They politely offered me an oil change I’d have to pay for  
 

I complained to GM customer care and setup an appointment with Chevy dealer across town. They replaced sending unit and all was back to normal. 
 

Original dealer must have gotten a call from GM because they called me and offered a free oil change as an apology. 

jaws3 Enthusiast

jaws3

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Good idea but not easy. Next dealer is 200km away from here...

redwngr Senior Enthusiast

redwngr

Posted
Posted (edited)

Aftermarket floor mats? 

 

Position sensor for skinny pedal loose or out of adjustment?

 

I'm not buying dealers 800 rpm soy either.

On the diesel sites lots have reported having the recall done -- no one has reported an increase in idle speed. 

 

 

Edited by redwngr
jaws3 Enthusiast

jaws3

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No aftermarket floormats. Everything as it was prior to the recall except the 800rpm. But thanks for corroborating that it is not normal.

redwngr Senior Enthusiast

redwngr

Posted
Posted

Good point ho

7 hours ago, hollywoodsle said:

image.thumb.png.0081ca072cbe96c063749b5018ad92c8.png

Good point.  

 

They can run high idle at startup, sorta like automatic choke on an old gasser.

And they can run higher for a reason like electical load, coolant temp and so on. 

They also will run higher shift points when cold.

 

My response was interpreting the op's description as never returning to a low idle once fully warmed to normal.  

 

curver900 Enthusiast

curver900

Posted
Posted

It will also run higher idle when Regen is active iirc on mine it is right around 800-900 rpm .  Make sure it completed a Regen.

 

jaws3 Enthusiast

jaws3

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Yes, idle never returns to baseline. This is not a "variable" idle rpm. It is over 800rpm all the time. Except at start up when it will idle at nase rpm  ut as soon as I drive off and stop the first time, it is above 800rpm and does not ho down until I shut down the engine

Edited by jaws3
Clarification
jaws3 Enthusiast

jaws3

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6 hours ago, white94rx said:

Your truck is in the middle of a regen. Drive it longer and when it's done the idle will go back to normal.

Sent from my Pixel XL using Tapatalk
 

Thank you white94. In my original post I stated this has been going  on for 2 weeks since the software update. It includes daily driving as well as a 1200km weekend trip. Surely that should be far enough? I have also noticed over the past 3 days TV that the gear change occuring just above 50km/h is very rough. As if the truck "jumps" at that changeover. Not sure if it is related but the truck is rapidly becoming very unpleasant to drive. Will make another call to dealer as that seems to be my only ootion. Apart from selling it.

curver900 Enthusiast

curver900

Posted
Posted
On 4/25/2020 at 11:31 AM, white94rx said:

That definitely should have been far enough. Mine usually takes about 20-30 minutes.

Sent from my Pixel XL using Tapatalk
 

Mine does it in exactly 20 miles if kept above 40 mph

jaws3 Enthusiast

jaws3

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1 hour ago, curver900 said:

A call to gm customer service is probably in order or have another dealer or this dealer reflash it

Have an appointment with the dealer next week to look at this again

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