Crazy idle

[K9Kodi]

My truck when it was cold out began idling like pure crap. It is a 2015 ram 2500 crew cab long bed 4x4. G56 tyranny and manual t-case. I never had an issue, then one day I started it and it idled with a terrible lope. It would idle fine, then drop to almost cutting off, then bounce right back. It would do it when it cold out, below 40-45. It was always a very consistent drop and rise. What I mean is it would always idle correctly for the same amount of time and drop rpms after a certain time, 10 seconds, and idle like crap for the same amount of time each time before going back to normal. I could hold it at 2k rpm and it would idle there, then drop to almost cutting off and go back to 2k. If I went to drive like this and started off giving it more fuel then it liked it would cut off and I would have to restart it, and it wild without issue. I ended up putting it in 2nd gear and just letting off clutch and idle around the neighborhood. It would surge now at the same time the idle would drop while parked. After about 2 minutes it smooths out and it's fine for the rest of day. One time I let it idle too long hoping it would warm up and it didn't stop. It just set of an engine light and message to check electronic throttle control. It cleared itself. It has been above 45 degrees in mornings for the last few days and he problem has not reared itself again. The pattern reminds me of grid heater cycling. I don't know what it could be, any suggestions?

 

[Ram4Sam]

Over on the CF awhile back, there was a thread about a rough idle situation. If I remember right... the cause was a defective valve of some sort in the high pressure side of the fuel system. I don't recall if it was a sensor, relief valve, etc. The OP of the thread it solved the rough idle. I searched for it once, found it, but don't remember exactly the search title I used, probably "rough idle" or something close to that.

Sam

 

[K9Kodi]

Thanks I'll check it oht

 

[sag2]

If you can duplicate it again at the dealer they will have to cold start it and monitor or record the fuel data to see what is changing. Anything else is just a guess.