Truck almost stalls out when cold start?

[MValdez]

I have 32K miles on my 5.7hemi longhorn and recently I have been experiencing really rough idle when I start her up and my truck literally almost stalls out. after 20-30 sec idle smooths out and then runs fine. Anyone experiencing this as well? suggestions?

 

[Fatherof3]

Has the temperature been fluctuating where you live ?

 

[Condor757]

Started a thread about just this issue last week with the same symptoms (thread title Cold Start Hiccups.) Another member posted this fix (from ANOTHER similar thread), and once I did it, the truck has been completely normal! Give it a try:

"OPTION TWO-RESET TPS & ACCELERATOR PEDAL (did once and works great so far)
1-Foot OFF of the brake and accelerator pedal
2-Press the START BUTTON until the RUN position is achieved but DO NOT start the vehicle. (If you do, turn off, open door and let everything reset before restarting).
3-Wait until all the instrument panels idiot/cycle lights go OUT (Check Engine light may stay on)
4-Slowly press the accelerator pedal all the way to the floor and then slowly let off. I think a steady and consistent motion is best.
5a-Press START BUTTON again to turn everything off. (Open Door?) Start the truck as normal. That should recalibrate the pedal so that you are using its full range of motion in synch with the throttle body's opening.
or
5b-Press Brake pedal and START BUTTON to start truck."

 

[bwsRam19]

My truck did this when new, and eventually stopped doing it before i could ever get it to the dealer

 

[Justin Avery]

I have a 2020 1500 Limited with the 5.7. I live in San Antonio and have had the same cold start, rough idle issue. Especially recently with the temps dropping to the 50s. I have a stock air intake box, other than a K&N replacement filter. I recently put in a friction modifier into the oil and a fuel system cleaner. I also use 93 octane. I know it's not needed and won't necessarily give me any benefits. Just like using it. At just 1000 miles on the odo, I shouldn't need any of that, however, after putting it in, my cold start issue has gone away. I also removed the secondary filter / mesh that was in the stock air intake box. Not even sure why that is there. I will also try the throttle re calibration and see how that helps. Even after the additives, I still get a rough idle and the truck searches for it's idle point for about 10 seconds.

 

[Condor757]

@Justin Avery

The throttle recalibration fixed my problem 100%. Give it a try and report back.

 

[Justin Avery]

I did the calibration yesterday. Had a cold start (57 degrees) this morning and truck almost died. I did the calibration process again and I'll see what happens tomorrow morning. Starts are fine after everything has warmed up. I really don't want to take it to the dealership. That probably won't be a good experience.

 

[Condor757]

Damn. Keep us posted

 

[GerryS]

Mine did that twice. The morning after driving from Illinois to Colorado it had a rough idle, and the same thing the morning after. I thought it might have had something to do with the change in elevation. It's been fine since.

Gerry

 

[Justin Avery]

So, update after doing the 2nd re-calibration, still had a rough idle, but not as bad. Outside temp only 67. Does anyone know of any service bulletins that are supposed to be done in regards to this issue? It seems like there is a computer mis-compare between the air, fuel and timing on start up. I've owned two Rams with the 5.7 before this, and never had this issue.

 

[Mopar_maxi]

So, update after doing the 2nd re-calibration, still had a rough idle, but not as bad. Outside temp only 67. Does anyone know of any service bulletins that are supposed to be done in regards to this issue? It seems like there is a computer mis-compare between the air, fuel and timing on start up. I've owned two Rams with the 5.7 before this, and never had this issue.

Took mine to the dealer Monday. Absolutely terrible experience. Had my truck sitting out back for 3 hours (while I was waiting). Tech got into my truck and pulled it around to the customer pickup line. Never once took it into the shop. I was told “can not duplicate customer concern” and advised to bring it back when it’s cold outside and leave it for the week. No thanks. Exactly why I HATE dealerships. So I’ll be ordering an unlocked PCM and tuner to fix it myself. FCA dealers suck.

 

[Fitz]

I recently had the rough cold start for about a month (even stalled twice during cold start). No change in cold start after recalibration of pedal. Finally went through enough gas and filled up at a different station. After the fresh gas, the cold starting issue was gone (good for a bit over a week now) and fingers crossed that it stays that way. I have been consistently filling up with 91 and I’m wondering if the premium fuel at the station I typically fill up at is not turning over as much lately. This is my first Hemi and I’m hoping the engine is just picky with gas and I don’t have to visit a dealer.

 

[Condor757]

There is a TSB for the rough cold start:

https://static.nhtsa.gov/odi/tsbs/2020/MC-10176547-9999.pdf