[kevinatfms]

I continue to have issues on cold starts. Start truck up in the morning or after sitting for more than 4 hours and it will surge from 750 rpm to 1000rpm.

From what ive done, found, tried:
-Fuel isnt the issue. Tried 15 different diesel stations. Tested 3 different diesel fuels from my own tank to determine if there is water in the fuel. Nothing wrong with the stations fuel in the tank but truck still surges.
-Diesel conditioner, anti-gel(both Diesel Power Services and Howes), 911 fuel stabilizer/anti-gel all do nothing to help the surge issue.
-Fuel filters may be clogged with water....no, replaced them every 5k miles from 35k miles to my now 45k miles with no change.
-High Idle switch in info screen does nothing. On/Off/Not selected makes zero difference in the idle quality.
-When the truck comes up to temp the idle will settle at the 3rd mark under 1000rpm and hold there like normal.
-Dealer has reflashed the truck 5 times with no change in idle quality when cold.
-No CEL, no stored codes, no indication lights. Nothing to lead me or the techs in any direction.
-Will do it whether i use the remote start, the key waiting for the glow plug light to go out, or with the key and just starting the thing. It all does the exact same thing.
-Truck drives fine once its warmed up. Idle surge does not happen over 45F.

I'm at my wits end with this truck. Issue after issue after issue keep popping up and the thing only has 45k miles on it.

Does anyone have a GM contact that wants to help get things looked into? I complained to Chevy Customer Care, they opened a case then its been crickets since. No call backs, no emails and no knowledge of any case with the dealer.

 

[valvecovergasket]

mine does this for a second or so when its really really cold following the tune... im surprised to hear this is doing it for the full length of the warmup, at not crazy temperatures, and stock as well

good luck! curious to hear what the outcome is

edit was just skimming the factory manual and didnt really see a general troubleshooting section... as most things are DTC driven. ill keep looking but yeah without a code itll probably be tough for the tech to start throwing parts at it.
id be hesitant to swap sensors as all of that kind of stuff is easily captured by set codes. has to be something more basic...

 

[Coloradocolada]

I’d throw in a new map sensor for the hell of it

 

[TheMuffinOfEvil]

This may be useful to you. I eliminated the throttle body on my diesel completely and it always does that on cold start now, exactly as you are describing.

I have no codes or anything because of my tune, but eliminating that is what caused it.

Diesel engines don't need a throttle plate, idle and acceleration is controlled by adding fuel. Our throttle plate is mostly used to choke the motor for emissions regulations, but my tuner told me that it was also expected to be there when doing a cold start, hence the surging idle for a half minute or more with it missing.

Also, it isn't really hurting anything beyond being annoying.

 

[dmaxjr]

Do you have elevated idle selected?. If so turn it off and select it again , . Sometimes it will cause a surge when cold temps.
Also just try leaving it off to see if it quits hunting on cold starts.

 

[papasmurf1958]

What dmaxjr said. My 19 idles at 750 rpm when remote started until I turn the key on. Then it goes to 900 rpm or so until it warms up. Idle stays elevated longer in cold ambient temperatures.


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[Jbomb001]

Mine surges when below 35 or so. For about a few seconds longer the colder it is. Up to 10 seconds if it 20. Like said before I dont think its hurting anything

 

[RedEyeB20]

I notice the same thing. Never thought of it as being a bad thing, just in the cold start portion of the ECU and never happens unless it is below 32°F

 

[kevinatfms]

What dmaxjr said. My 19 idles at 750 rpm when remote started until I turn the key on. Then it goes to 900 rpm or so until it warms up. Idle stays elevated longer in cold ambient temperatures.


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Its not the high idle. I’ve done everything possible and it doesn’t change anything.

 

[kevinatfms]

Do you have elevated idle selected?. If so turn it off and select it again , . Sometimes it will cause a surge when cold temps.
Also just try leaving it off to see if it quits hunting on cold starts.

It’s not the elevated idle. I’ve tried every variant possible and so has multiple dealer techs over multiple days at the dealership.

 

[Jbomb001]

It may annoy you but I dobt think its really a problem. From what I'm experiencing and what I've read i think ... now hear me out... diesel doesn't like cold weather? Not trying to be a smart ass. Just don't think your going to find a solution till spring.

cold diesel surging - Google Search

 

[papasmurf1958]

There is a setting on the 2019 in my infotainment center but changing the setting does nothing. Its a normal malfunction. Nothing to worry about.


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[Harobmxer87]

Mine has done the surging idle in the past on cold mornings, even stalled a couple times. Would go away and idle normal once warm. Hasn't done it in a couple years though. Feels like it's just one of those "nature of the beast" type things. Not sure if there's really any solution.

 

[Jbomb001]

Changing the high idle does do something. It raises your idle by 100 rpm. Its just to help it warm up. Won't really do anything for the quality of idel however.

 

[kevinatfms]

It may annoy you but I dont think its really a problem. From what I'm experiencing and what I've read i think ... now hear me out... diesel doesn't like cold weather? Not trying to be a smart ass. Just don't think your going to find a solution till spring.

I know diesels dont like cold weather but that has nothing to do with the issue at hand. If there are trucks in COLDER climates that have zero issues starting it isnt the cold. There is a malfunction in the truck that needs to be rectified.

This isnt my first rodeo and certainly isnt normal.

 

[kevinatfms]

Mine has done the surging idle in the past on cold mornings, even stalled a couple times. Would go away and idle normal once warm. Hasn't done it in a couple years though. Feels like it's just one of those "nature of the beast" type things. Not sure if there's really any solution.

Nature of the beast? Sorry to say there are plenty of people running these trucks in temps nearly 50 degrees colder than i am without a single issue. Its not normal or "nature of the beast". There is a problem and i guess instead of just chalking it up to "diesel issues" ill figure it out and post it up.

 

[kevinatfms]

What dmaxjr said. My 19 idles at 750 rpm when remote started until I turn the key on. Then it goes to 900 rpm or so until it warms up. Idle stays elevated longer in cold ambient temperatures.


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But your idle stays at 950 during that warm up?

Mine will start surge from 750 to over 1000rpm back and forth, back and forth, back and forth until the truck is fully warmed up. That is nearly 15 minutes of surging idle. If the truck idles smooth at 950rpm without surging, that is completely understandable as its an elevated idle to warm the truck up. Mine does not hold an rpm during warm up.

 

[Coloradocolada]

Does the surging stop once it goes into gear?

 

[Coloradocolada]

Does the surging stop once it goes into gear?

 

[kevinatfms]

Does the surging stop once it goes into gear?

No. It will surge in gear also. Its enough of a surge that it will almost overpower the brakes. Hence why i know this is not normal.