Hello, I was looking for some advice on my 2005 Limited Hemi Durango. Recently it has been developing a misfire problem that I have not yet been able to diagnose. When the car is cold the misfire is not very noticeable but increases in severity as the car is driven. Running around the city it will idle rough and have a noticeable loss of power. If taken on the freeway and cruising around ~70mph the misfire will get very severe and cause the check engine light to flash relatively often (Every 2 - 5 mins) and appears to get more frequent at lower RPM (Around 1800), however once the light stops flashing it does not remain illuminated until it begins to flash again. Usually after it gets real upset on the freeway it will run exceptionally bad during idle and driving until it sits and rests for awhile. I have taken it into a shop and they were unable to diagnose the issue and recommended I pay to have it put on a dyno and scoped. I am skeptical of this solution because the mechanic also said he was unable to retrieve misfire data from the car, which I am able to retrieve using a $23 Bluetooth OBDII scanner.

So far I have been trying to learn how to use the Torque app with this scanner to help me diagnose the problem. When looking at the misfire data cylinder 4 has the most historic misfires recorded (~1600) and a few other cylinders are reporting around 20-30 historic misfires. Also when looking for stored codes I am not able to find any pending codes that relate to misfire. Furthermore the scanner is indicating the O2 Bank 2 Sensor 1 has low current and the app indicates that it is a problem.

Finally the D has 165000 miles on it, and has received all required maintenance at this point. The last tune up was done about 26,000 miles ago by the dealer, however I believe the coil packs were not replaced during this tune up. During the misfiring the intake manifold was cleaned and the gaskets were replaced. This removed the P0174 that was being thrown however does not seem to have made a change to the misfire at all.

I had planned to grab a coil pack and try that first however I would greatly appreciate any input on this.

 

One thing you could try is to swap the spark plug and coil wires with another 'good' cylinder and see if the missfires move to the 'good' cylinder. By swap I mean take wires completely off bad cylinder, take wires completely off good cylinder, put good wires onto bad cylinder, put bad wires on good cylinder, so that firing order is not changed.

If the missfires move to the good cylinder and missfires greatly reduce on 4 then you have a bad spark plug or coil wire.

You might also check that the wires are routed correctly in the first place.

 

Replace the O2. It will cause dumb things to happen but is probably not the problem. Sounds more like a head problem if moving the coil doesn't change things. A valve could be sticking or the lash adjusters could be worn. Had that problem on my limited on #8. Actually threw the rocker off. Could be other things but at 165k you are in the timing of the valve mileage. And if your running with a hard mis, flashing light, your going to ruin the engine or cat.