Cylinder #5 misfire P0305

[rwfnetworking]

2012 Ram 1500 Sport 145,000 miles. Been having CEL P0305. More noticeable under load. Originally diagnosed as bad rings with low compression at local shop. Until they wanted $14,000 for a engine replacement.

Finally got it home and did a compression test. Result was 180 psi. So, obviously the mechanic must if been stoned when diagnosing. I'm going back with my assumption that this is possibly a cam/lifter issue as coil pack, plugs and fuel injectors were swapped and tested good, but I will be double checking as the local shop who diagnosed this also verified the integrity of the plugs, coil pack and fuel injectors. What's the best approach to know for sure what the issue is?

Robert

 

[Burla]

Pull the valve cover...

Hemi 5.7 P0305 Cylinder 5 Misfire - Dead Cam/Lifter

Diagnosing a P0305 cylinder 5 misfire code on my 2011 Ram 1500 Sport 5.7 Hemi. Replacing spark plugs and coil pack did not fix the issue. This was the start ...

youtu.be

 

[mtofell]

Are you getting a flashing CEL or just the code? I started with a flashing light and then a similar code (may have been a different cylinder #) and ended up needing an engine due to a failing bearing and metal shavings but from talking to the dealer and folks here my situation was pretty rare. Just throwing it out there as something to keep in mind.... REALLY hope it's not your situation.

 

[rwfnetworking]

Are you getting a flashing CEL or just the code? I started with a flashing light and then a similar code (may have been a different cylinder #) and ended up needing an engine due to a failing bearing and metal shavings but from talking to the dealer and folks here my situation was pretty rare. Just throwing it out there as something to keep in mind.... REALLY hope it's not your situation.

I actually get both. Normal cruise driving the CEL will be steady, but under heavy load when accelerating it will start to flash. I've read similar posts with those symptoms where the problem ended up being a bad lifter and damaged cam.

 

[Shepherdguy]

Is your truck driving smooth and then the CEL start flashing once you reach approximately 2500 rpm's? Unless you already solved the problem, try doing some test drives and keep your rpms below 2200. It is going to want to shift gears around the 2000 rpm range and by doing this, you're going to feel like there is a bit lack of power but thats because the hemi wants to travel faster than that. But keep it under 2200 for a few test drives. On a scan tool, you may still see some cylinder 5 misfires, but you won't feel it much or at all. If your test drives do not throw a flashing CEL (pending DTC) or a solid CEL (stored DTC), then the mechanical issues are less likely your problem. You may want to consider the PCM, but rule out everything else first. Mechanical issues will show up in a direct compression test, leakdown test, and/or a relative compression test. I am assuming you have already done the basics (swapped or replaced spark plugs, swapped coils, and swapped injectors with the problem remaining at cylinder 5. Also check your coil and injector plugs. If the PCM is the problem, you may be able to use a low voltage test light to back probe the coil connector to test for consistent pulse at the higher rpms. If you get missed pulses, test at the PCM harness by back probing (need wiring diagram for proper wire). if the signal is still inconsistent, it's going to be your PCM, if its consistent at the PCM, then there is going to be an issue in the wiring. most likely at the connector. Ideally, this test would be done with a scope but most people don't have scopes. Often times when someone changes the spark plugs, they hold the clip on the connector in and pull on the wires to pull the connector off the coil, risking damage to the wires. If the wiring is damages enough to short across the ground and signal wires, it can damge the driver in the PCM. But like I said, rule everything else out first before condemning the PCM.