2012 Ram 1500 Hemi Cylinder 3 Miss Fire

[JWehr]

I have a 2012 Ram 1500 with the 5.7 Hemi. I am getting a Cylinder 3 miss fire. I have swapped the firing control module with cylinder 5. Error code occurred again. I replaced the plugs in cylinder 3. Error Code occurred again. I swapped the firing control module with cylinder 4. Error Code occurred again. Looking for suggestions on what to do next before taking it in for diagnostics. Symptoms, rough idle on start after high idle and RPMs drop to normal idle. Idles rough any time I am not moving under vehicle power. Sometimes the rough idle is less to almost non existent. I did run injector cleaner through during 2 fill ups. Any suggestions are welcome.

I have a new 2022 Ram 2500 with the 6.4 and 4.10s sitting in the drive. But I would like to fix the 2012 and then sell it.

Thanks

 

[HuskerRam]

Sounds like you lifter & camshaft may be toast. Have you pulled the valve cover to see if the rockers are moving when you turn the engine? If that rocker doesn’t move, then the source of your problem is likely lifter & cam.

 

[JWehr]

I have not pulled the valve cover. If the cam shaft or lifter was bad, would I experience a rough idle and would the truck run rough when driving? When I am driving there is no noticeable vibration.

 

[crash68]

If the cam shaft or lifter was bad, would I experience a rough idle and would the truck run rough when driving?

The cam for that cylinder maybe worn to the point your just starting to get misfire codes, it will most likely get worse.
Did you try swapping the fuel injector for that cylinder? If you've already tried swapping the ignition coils and changed the plugs, about the only things left are valves and piston rings. You could do a compression test to rule out the rings.

 

[JWehr]

I have not swapped or replaced the injector. Got a automotive stethoscope, the injector sounds like it is firing but doesn't sound like the rest. May take it in for some diagnostics. When driving no issue. The issue is present upon start when idle drops from high idle to normal idle and when sitting at a stop sign or red light.