MP9C
Junior Member
Hey everyone, First post here due to my newly acquired Ram.
Specimen on hand
2011 5.7 Bighorn
190k
Maiden voyage was 2.5 hours across the state pretty much without issue.
Ended up with a o2 sensor code for a bad sensor and a P0308 for a bad coil. The old sensors looked original so they were all replaced, and a new coil was needed on cyl8 all was good.
The next day I ended up with a P0300 and I have been chasing it ever since “roughly 2 months”
So the P0300 consist of misfires on cylinder 4 and 6
I have changed plugs, changed coils, cam sensor, crank sensor, Intake gaskets, I have pulled a valve cover to look for broken springs, damaged rocker arms to find nothing damaged.
I have also rotated the motor over by hand to measure the max lift of the cam through the rocker ratio from the rocker boss in the head to the peak of the rocker arm and they all measure the same So I am assuming the cam is fine.
I have also pulled the pushrods to make sure that nothing was damaged or tweaked to find nothing.
Also rotated injectors and the miss didn’t move.
Compression is 175 175 160 190 so yeah I know 6 is the weakest but it’s still within spec I also performed a wet compression test and all cylinders are over 300psi so that should rule out a bad seat or a burnt valve
I did notice while testing and running the engine, when it’s missing the worst it seems the coils on 4,6 have lost their - pulse trigger from the pcm
So just replaced the PCM had it updated with the most recent flash from Chrysler and had everything re-calibrated to the new PCM for it to not help at all.
I even added a heavy ground from the engine to the chassis wondering if that would help.
So when cold it runs great, once warm at an idle it sucks but if you stay driving at a normal pace or Highway it runs perfect but in stop and go it’s a mess.
I have done a lot of testing thus far but I am looking for any insight that anyone might have.
Thank you in advance.
Specimen on hand
2011 5.7 Bighorn
190k
Maiden voyage was 2.5 hours across the state pretty much without issue.
Ended up with a o2 sensor code for a bad sensor and a P0308 for a bad coil. The old sensors looked original so they were all replaced, and a new coil was needed on cyl8 all was good.
The next day I ended up with a P0300 and I have been chasing it ever since “roughly 2 months”
So the P0300 consist of misfires on cylinder 4 and 6
I have changed plugs, changed coils, cam sensor, crank sensor, Intake gaskets, I have pulled a valve cover to look for broken springs, damaged rocker arms to find nothing damaged.
I have also rotated the motor over by hand to measure the max lift of the cam through the rocker ratio from the rocker boss in the head to the peak of the rocker arm and they all measure the same So I am assuming the cam is fine.
I have also pulled the pushrods to make sure that nothing was damaged or tweaked to find nothing.
Also rotated injectors and the miss didn’t move.
Compression is 175 175 160 190 so yeah I know 6 is the weakest but it’s still within spec I also performed a wet compression test and all cylinders are over 300psi so that should rule out a bad seat or a burnt valve
I did notice while testing and running the engine, when it’s missing the worst it seems the coils on 4,6 have lost their - pulse trigger from the pcm
So just replaced the PCM had it updated with the most recent flash from Chrysler and had everything re-calibrated to the new PCM for it to not help at all.
I even added a heavy ground from the engine to the chassis wondering if that would help.
So when cold it runs great, once warm at an idle it sucks but if you stay driving at a normal pace or Highway it runs perfect but in stop and go it’s a mess.
I have done a lot of testing thus far but I am looking for any insight that anyone might have.
Thank you in advance.