2006 Durango, V8 4.7L 171k miles.

Ok, this one has me stumped. I have an idea, but wanted to get some other input. Wife calls me yesterday (it's her DD, btw) and says that the truck was acting really bad and she barely made it home. Upon inspection, I found a few things. From her explanation, I was thinking misfire and cylinder loss because of it. Checked the codes and there was not anything but a grey cylinder 5 misfire code. It had not tripped the CEL. Thought this was strange as she said it was running terrible on the way back which was about 10 miles.
Took it out myself and finally have some better symptoms and they are quite specifically weird.

Starts no problem. Idles great. Fluids are all good. Driving around town, it drove fine. Power good, etc. Then I was able to get it to exhibit the symptoms. I was driving about 45 on a straight road and as the incline of the road increased, I held the throttle steady and RIGHT at the point that it shifts into overdrive I heard and feel what I am certain is after-fire in the cat. It feels it is right under my feet on the drivers side. Power loss at this point wasn't that noticeable if I pressed harder on the gas, I wasn't really feeling any misfire, just hearing and feeling the ignition in the cat. No codes at all. If I let off the gas and coasted, the symptoms stopped.

Unsatisfied, I went to an even longer, more gradual and steeper hill. One that wouldn't kick down a gear, but I could go fast enough to accomplish 2 things, get it to go into OD but also have more load by way of the hill. I hit the jackpot here (always seems strange WANTING a code).

Right about the same speed and just before OD kicked it, I felt a little shudder and then the cat ignition. As I kept it steady, it got worse and DID finally start misfiring and the CEL finally did come on. I did feel a loss of power, but nothing major..basically 1 cylinder worth of power loss.

On the way back to the house, there was a hill that I went down and I gave it quite a bit of gas going down the hill and the symptoms didn't show up. So it certainly does it under load, but had I gone up the hill with more gas, it may not have done it (based on the testing I did).

Checked the codes and had a P0300 and P0305. I should note that about 3 years ago, we had the same symptoms and I changed the plug initially on cylinder 5 and that didn't do anything. Then changed the coil and it seemed to fix it. I had other issues with misfires on cylinder 7 randomly (but without the ignition and felt misfires) for a couple years. In september, I changed all plugs, and 5 and 7 injectors which made HUGE difference in performance and solved the Cylinder 7 misfire codes.

Back to this issue. I swapped the 5 and 7 coil to hopefully get the same issue, but this time on cylinder 7. I also checked the plug on 5 and it looked great. only an insignificant amount of clean oil on the thread. Very slight amount.

Drove the same route, the same way, and sure enough it exhibited the same symptoms, except this time, the misfiring and power loss and shuddering were much much worse. It always seems to start as cat ignition just before it all goes haywire. BUT..no CEL, at all. I couldn't believe it, this thing likes to throw codes like nothing, so couldn't figure out why it wasn't.

Pulled codes anyway and had a pending fault for a P0300 again and a grey P0300 fault, but no mention of a specific cylinder. I figured a coil is only 25 bucks and it fixed it before, so I threw that part at it. Immediately after doing so, I unfortunately got the same cat ignition, but didn't really feel a misfire or cylinder loss. Pulled the codes..nothing at all. Dammit. Then, I went out after letting it sit for about 20 minutes to get some food. On the way back, I decided to go up the hill that made this problem crop up every single time without fail. THIS time, it ran perfectly. No issues whatsoever. Dammit again. (I need something definitive, if you know what I mean!).

For other reasons, I have always had a sneaking suspicion that I have had some sort of cat problem. It is not necessarily exhibiting clear signs of cat problems (lack of power, stalling, sulfur smell, etc.); however, if I don't have them fully now, with all this after-firing and the years of random misfires especially on that side, it can't be in the best shape.

So 2 questions - Any thoughts on what the firing problems are related to, because I am at a loss.

Secondly, I think that if for nothing else other than peace of mind and knowing the cats are not a problem, I want to do something with them. Being that is is Christmas season, and the fact that my oldest son is graduating Basic Training next weekend and taking the trip there is expensive, I need a cheap, quick option until I can do something more permanent after the first of the year.

I can't really afford even universals right now. I am not interested in any performance gains or sound, ,etc. Just eliminating problems. So that means my options are having them removed and straight-pipe welded in. We do not have emissions testing here, so not a problem there. I would have to take it to a local exhaust shop around here to have this done as I don't have any way to weld it, and from what I can see on these cats (both of them), there isn't an easy way to cut and clamp the manifold side. I figure this would be pretty cheap, but not sure they would be OK with doing it.

I could also gut the cat which I am willing to do, but since these are bolt on on one side and welded to the other side, not sure how easy this would be. Again, I could cut the window, but would still have to get someone weld the piece back together (thinking, might as well just re-pipe it if doing this).

Does anyone have any suggestions, tips, etc. on dealing with the catalytic converters? Thanks!

MIke

 

It sounds like it certainly could be a partially clogged/clogging cat.....

Exhaust shop won't do anything aside from test, or replace them. They can't legally remove them, without putting new ones in place. They may have some cheap alternative....... but, I don't think they can get away with doing "test pipes" any more......

Which side of the cat are the bolts on? Upstream, or down?

 

Man, I can't believe I wrote all of that from my phone! Didn't realize how long the post was, so thanks for sticking with it!

I find it strange that if we have no emissions regs where I live (not even in the state, well except Northern VA, DC Metro area) they can't do this. I do live in a somewhat rural area, so really all I need to do is find someone who will weld it for me I have an uncle about an hour away who has a personal garage, lift, and my brother can weld, so maybe I have a solution for now.

Anyhow, it bolts at the upstream only - to the manifold. Actually, now that I think about it. I suppose I could unbolt it, and then cut it where the pipe straightens out. Gut them and then just use clamps for now. I have several options.

Wife drove my daughter to school this morning in it and said it didn't thrown any fits, though there is a short but steep hill on the way and she said it felt as though it didn't have much power going up that hill. I will be testing more when I get home. I thought maybe she was driving it a bit gentler since she may have been worried the issue would crop up again.

Thanks again!