Sub-Zero temps and P0300

[KarL45]

Cold weather misfire and code

If the vehicle is a 2013, would recommend taking it to the dealer. The computer will store the code and probably other information leading to the code. If not, it may be hard to tell exactly what the cause is without guessing. One slightly fouled plug, wire, would be guesses. Just a thought, is your coolant level at the "COLD FULL" line before starting? Have seen slight coolant leaks, on one cyl only, cause a cold weather, short term misfire. Doubt that's it but if coolant loss is suspected as well, could be.

 

[akvulcan]

I have had the same issue on my 2018 2500 6.4L for two years. I live in Alaska. I park my truck outside and use a block heater whenever the temp < 20 deg. When the temp drops below 15 deg. the truck misfires and throws an P030x code with flashing CEL shortly after startup. By the time I drive it to the dealer the truck warms and the misfire and light stops. In order to recreate the problem I have to leave it at the dealer overnight on a cold weather morning. The dealer has recreated the problem multiple times on cylinders 2, 4, and 8. On #2 they replaced the ignition coil and two fouled plugs but that didn't fix it. It's now back at the dealer for the third time and has been turned in to a FCA "Star" warranty case with factory involvement. It's been at the dealer for three weeks this winter with this problem. I use Holiday 89 mid grade gas, but here in AK we only have one refinery so all of the gas comes from the same place regardless of where you buy it, and it is all a gas / ethanol winter mix. I'm about ready to go the lemon law route with this one.

 

[RedSRT4Me]

I have had the same issue on my 2018 2500 6.4L for two years. I live in Alaska. I park my truck outside and use a block heater whenever the temp < 20 deg. When the temp drops below 15 deg. the truck misfires and throws an P030x code with flashing CEL shortly after startup. By the time I drive it to the dealer the truck warms and the misfire and light stops. In order to recreate the problem I have to leave it at the dealer overnight on a cold weather morning. The dealer has recreated the problem multiple times on cylinders 2, 4, and 8. On #2 they replaced the ignition coil and two fouled plugs but that didn't fix it. It's now back at the dealer for the third time and has been turned in to a FCA "Star" warranty case with factory involvement. It's been at the dealer for three weeks this winter with this problem. I use Holiday 89 mid grade gas, but here in AK we only have one refinery so all of the gas comes from the same place regardless of where you buy it, and it is all a gas / ethanol winter mix. I'm about ready to go the lemon law route with this one.

I have experienced this off and on since 18 when I changed my stock plugs to colder ones. My truck is a 2015 5.7.

When it is 115° F out I have zero problems. When we start getting towards 40° F "save the jokes" I get the misfire cel. Once the truck is warm the misfires are gone. If I travel to Colorado at 10,000 ft elevation the truck will also stumble during initial start up.

For me I think once I get back to stock heat range plugs all will be fine.

My theory for cold climate folk in the winter is switch to a 1 step hotter plug. Either that or Ram can diagnose your log and issue an update to their startup calibrations.

 

[RedSRT4Me]

Last but not least. The gas is just water nowadays and we just have to put up with it realizing it's not a permanent break.

 

[akvulcan]

Latest update on my RAM 2500. Chrysler this week had the dealer pressure test the cooling system (OK) and yesterday the dealer called me to get authorization to clean the fuel injection system (at my expense; they say this is a maintenance item). The adviser told me that this is the next step in the troubleshooting process and it may or may not work. My truck has now been in the shop for 21 days this time and over thirty days this winter on three separate occasions and it sounds like they have still not found the problem.

 

[akvulcan]

The dealer released the truck to me after doing a fuel system flush. The told me that several days of testing in cold temps showed that the problem did not reoccur. I've had it for three days and all is well.