I have a 2008 Dodge Dakota 3.7 V6 with 165,000 miles. A few months ago the check engine light came on and the truck had a rough idle. I checked the usual suspects and some unusual ones. When I pulled the code, it threw p0305 (Misfire on cylinder 5). To diagnose, I swapped coilpack from 5 to 3. Threw the same code the next day. Swapped plug from cylinder 5 to 3. Same code right away. Ordered a new injector from Rockauto. This is where it gets interesting. When I installed the new injector, the truck went from an occasional miss and rough idle to a dead miss. Still showing p0305. Drove the truck about a mile and truck was obviously missing. No power, shuddering, and check engine flashing. Put old injector back in and the truck still acted like it had a dead miss with the same code. Drove the truck about a mile and it went back to having an occasional miss. I've sense done a compression test, checked fuel pressure, and flushed fuel rail (to make sure there was no water stuck in rail). I don't remember what the compression was exactly, but all 6 cylinders tested the same and were what the repair manual calls for. Fuel pressure was normal as well. Checked continuity on injector harness and coilpack harness. Both looked to be good. The truck is still acting up occasionally. Any other ideas? Thanks in advance for any help.

 

Any resolution to this problem? I seem to be having the same issue. Replaced plugs, swapped coils, still stayed with cylinder 5. Took it in to a shop and they replaced injector and pigtail. Same situation though, shop thinks it's PCM but I might do a little more troubleshooting before I go replacing it.

 

Per review of the service manual, please review the following:
When a Misfire is detected for a particular cylinder, the PCM will shut down that cylinder's Injector Control circuit.
1.Visually inspect the engine for any of the following conditions:

• Worn serpentine belt
• Binding Engine-Driven accessories: A/C Compressor, P/S Pump, Water pump.
• Misalignment of the Water pump, P/S Pump and A/C Compressor pulleys
• Corroded PCM power and ground circuits.
• Improper CKP, CMP, MAP and TP Sensor mounting
• Poor connector/terminal to component connection. i.e., CKP sensor, Fuel Injector, Ignition coil, etc.
• Vacuum leaks
• Restricted Air Induction system or Exhaust system.
• Internal engine component failures.

If everything checks out then the following can be possible causes:
(A955) ASD RELAY OUTPUT CIRCUIT;(K38) INJECTOR CONTROL NO.5 CIRCUIT;(K16) COIL CONTROL NO.5 CIRCUIT
SPARK PLUG; IGNITION WIRE; IGNITION COIL
FUEL PUMP INLET STRAINER PLUGGED;RESTRICTED FUEL SUPPLY LINE; FUEL PUMP MODULE; FUEL PRESSURE LEAK DOWN;FUEL INJECTOR
ENGINE MECHANICAL PROBLEM
POWERTRAIN CONTROL MODULE (PCM)

Hopefully this will provide some additional things to check and you may need a service manual to further troubleshoot.