P2305 on a high mile 2008 4.7

[3pedals]

Truck is a 2008 ram 4.7 6spd with 420k miles. After being parked for a couple weeks (ran perfect when parked) is now throwing a p2305 “ignition coil 2 - secondary circuit insufficient ionization” code. This misfire only shows up when engine is relatively cold, and after a few miles of driving seems to run perfectly. Swapped coil and plug wire (from coil to lower plug) with another cylinder and no change…same misfire and same code.

Spark plugs are OE/Bosch and only 20k miles old. All 8 original injectors were replaced with new OE/Mopar for other reasons (leaking gas = rising oil level) about 6 months/10k miles ago.

The truck runs as well as it ever has for the most part, except when engine is cold or truck has been parked for a little while (engine oil & coolant still warm, but perhaps other things cooled down). Almost like there needs to be some more heat in the engine compartment for the misfire to disappear.

Any ideas on what to look for next?

Will be taking in to a trusted shop next week if I can’t figure out fairly easily…

 

[HydroDog]

I would do a compression test and see it it’s low in that cylinder. If it is I would pull the valve cover off and see if you have a sticky lifter.

If the compression is equal against checking a couple other cylinders I would check the two spark plugs. I have had bad ones before. Might also double check your electrical connection on the injector also.

 

[3pedals]

So, it’s fixed (for now) but don’t know how or why. Took it to my trusted local shop, and they messed with it some more. Finally had the idea to pull the #2 coil, pull the spark plug, stick the plug in the coil, and see if the damn thing sparks. Well, my mechanic had a brainfart and was holding the plug while doing this test and got zapped pretty good (and yes it sparked lol). Put it all back together and called me to say he couldn’t figure it out.

From that moment, the misfire & coil codes seem to have disappeared, and the truck runs beautifully.

 

[3pedals]

And the misfire is back. Ran great for several weeks and now the sporadic misfire has returned. It’s almost like an on/off switch…truck will miss on one cylinder for several minutes, then run perfectly for several minutes, and so on.This problem arose a couple of months after the dealer pulled my transmission and had it rebuilt/reinstalled. Is there something dealer could have knocked loose that could be a potential cause?

 

[3pedals]

Problem solved…bad pcm. Plugged in a spare pcm and truck runs on 8 angry cylinders again! Would like to have original pcm repaired to keep as a spare on the shelf. Any recommendations on where to have this done?

 

[jws123]

Problem solved…bad pcm. Plugged in a spare pcm and truck runs on 8 angry cylinders again! Would like to have original pcm repaired to keep as a spare on the shelf. Any recommendations on where to have this done?

Glad ya fixed it and DAM 400k+ miles is that the orig engine? If so thats the most ive seen on a 4.7 they usually blow around 200k or so i rebuild them often.

 

[3pedals]

Original engine replaced by Chrysler under LPT warranty at a little over 300k miles. It probably didn’t need to be replaced, but was starting to burn oil from valve seals, and upon inspection rockers were worn and all valve springs were “squished”, as in they wouldn’t return to full extension. Cylinders still had visible cross-hatching and would have been fine with a valve job, but Chrysler opted to replace the engine due to mileage. Didn’t want to argue with that…

To be fair, truck has always been driven extremely hard with a lot of high rpm and heel/toe downshifts since I bought it new with 8 miles. Other than the fuel economy (put well over $100k worth of 87 thru it), this truck has been remarkably reliable given the use. Don’t know if the newer 16-plug 4.7 is that much better or if I just got lucky