2017 5.7L HEMI Cold Start Stumble

[fernandok]

Vehicle: 2017 Ram 1500 5.7L HEMI 60k miles or so.

I have had this problem on every single cold start for the last year or so. The truck will crank and start up without hesitation or problem, once the engine begins to cold high at 1600-1800RPM as normal it'll stumble like a misfire, leaking injector, etc and drop down to 900-1100RPM for approximately 2-3 seconds and then smoothen out and go back up to 1600-1800RPM. This all happens in less than 5 seconds from cranking to post-problem.

I can duplicate it every single time on cold soak start overnight. If it sits at work for 4 hours and I go for lunch, it doesn't do it.

Nor does it ever do it on a hot start.

Anyone else experience this?

 

[1999 White C5 Coupe]

Vehicle: 2017 Ram 1500 5.7L HEMI 60k miles or so.

I have had this problem on every single cold start for the last year or so. The truck will crank and start up without hesitation or problem, once the engine begins to cold high at 1600-1800RPM as normal it'll stumble like a misfire, leaking injector, etc and drop down to 900-1100RPM for approximately 2-3 seconds and then smoothen out and go back up to 1600-1800RPM. This all happens in less than 5 seconds from cranking to post-problem.

I can duplicate it every single time on cold soak start overnight. If it sits at work for 4 hours and I go for lunch, it doesn't do it.

Nor does it ever do it on a hot start.

Anyone else experience this?

Since this has been occurring for at least a year, did you take it to the dealer for diagnosis and repair under terms of the power train or emissions warranty?

 

[fernandok]

Multiple answers of "it's just a hemi" thing.

Seems like the common answer for any and all problems with these trucks.

 

[Burla]

Are you talking cold as in freezing? Our trucks have a myriad of sensors adjusting the fuel air mix, when you shut the truck down they have adjusted to that condition, so when you start a truck and it is cold you can have more o2 in that fuel/air mix til the truck adjusted. Have you tried 91 octane? if it is more o2 in cold air this can solve that.

Fuel,Air,and Spark are the considerations and add only happens when cold. So when you talk about spark, batteries are less effective in the cold and could be the issue here, as it gets more charge form alt, you wouldnt see it. I'd dump sea foam through vac lines and clean out combustion chamber, and maybe more importantly run some redline si-1 through the gas tank in case it is fuel atom issue with injectors, it is at least possible it can be clogged injectors more of an issue at start up. It wouldn't be a terrible idea to get new plugs if you havent yet. run codes, something might pop up.

You say a year, but if you think back, did it always do it when it was cold?

 

[fernandok]

Cold soak cold start just means sitting overnight or for more than 8+ hours before starting. Happens the same in summer or winter, ambient temp is irrelevant.

I've always ran Shell 91 since new.

No codes.

I'm leaning towards a leaky injector.

 

[Burla]

Yeah, could be clogged and not atomizing, worth a try running redline si-1 though, I say that one seams to be effective, amsoil pi, rp treatments, techron all have PEA which is the best known injector cleaner. It is a specialized detergent. Nothing to loose but a couple bucks, much to gain. We had a ram forum member boroscope his combustion chamber after running si-1. This was just after one treatment I believe, he had before and after pics, you can see it melting away baked on carbon on piston top. It would be cool if this solved it.

Redline si-1 also has esters so those also clean..

 

[fernandok]

I'm a master tech for Honda, but I figured I'd ask here in case anyone else experienced something similar.

It's most definitely a fuelling issue.

This morning I gave it a boot-full as the stumbles started happening and it backfired out the intake manifold. I heard it through the intake box. Lol.

Shame here is no exact way of telling which injector or injectors are the culprit. Data list on my scan tool doesn't pick anything up. Unless I run noid lights on each injector and watch the pulses. Because at $99/ea I don't want to spend $800 for all 8.

 

[Coytet]

Was this ever sorted out. I have a 2022 5.7 in Australia doing the same thing. It's been at the dealership for a total of 18 weeks so far they've replaced. Fuel pump, full set of injectors, pcm, swapped out throttle body and 4 02 sensors all under warranty now they ave stated " the cold start stumble is a feature not a fault"