Hello everyone,
I'm new to the site and I'm needing some diagnostic assistance. I've got a 2005 Hemi ram 4x4 with 110xxx miles on it. Lately I've been getting P0300 (random misfire) and the truck has been missing badly. At first I thought it was water in the gas as I had filled up at wal-mart while the re-fuling tanker was there but I've been through 5 tanks of gas and 4 bottles of heet water remover and the problem is still there. I am getting no other codes to help me narrow this down either. What happens is when I am cruising and go to accelerate, the truck will just bogg down, like it's not downshifting. But if I smash the gas it will downshift and take off just fine. Lately it has gotten worse and it starts missing even when I'm cruising with no acceleration at all.

I've been doing some reading online and it seems like the EGR valve might be a suspect, but I haven't gotten a code for it. Tonight I plan on inspecting the wiring harnesses and checking for any cracked or disconnected vacuum hoses. Are there any other things I should be looking for? Just had a tune up 5000 miles ago (air filter, plugs, wires). Thanks for the help.

John

 

Also the fuel mileage has gotten progressively worse since I bought it 5 months ago. Currently I'm getting sub 12 mpg.

 

Engine? 3.7, 4.7 or 5.7?

It'd be rare at best for a bad EGR to cause a misfire, but it sure will cause poor gas mileage.

I have my strong suspicions, but need to know what engine first...

 

Hi Hammer....Just re-read the OP's post and he says in the post title
"2005 Hemi ram misfiring badly"
So I think he has a Hemi....5.7?????

Not being sarcastic........honestly

So post upu what you think it is Bro'.

Al.

 

Throttle body clean, new plugs (and wires if it uses them), PCV valve clean/replace, air filter.

 

No other codes then I would be looking at the PCM or the connection to it. Hopefully your PCM is not faulty because its an expensive part to replace just had mine done with all 8 coils too.

 

With 110k on it, when was the last spark plug change done? EGR is a possibility. There was a guy not too far back that was getting P0300 also and said he changed his front O2s and it resolved it. Bad O2 could give bad mileage also. They are $25 at autozone. I recently replaced both my front O2s as well.

 

Also check the wiring harness like you said for fray or cut wires. I just went through a simular issues myself with major shudder under load and backfires.
Codes were continuous.
P2317
Ignition Coil 6 Secondary Circuit-Insufficient Ionization"
P2305-IGNITION COIL #2 SECONDARY CIRCUIT-INSUFFICIENT
IONIZATION
and a few random misfire codes.
Realized there was no power going to the those coils so i pulled the harness and check and there was sliced wires. fixed them up and wallah.
Power back like no other and then some.

 

Well I just did the plugs less than 1000 miles ago. We ran a few "tests" the other night, I unplugged the EGR sensor so it would run in limp mode with the CEL on constantly and the problem went away for the time being. The next day it came back even in limp mode. So I finally caved and took it to the shop to be scanned and the results weren't pretty. According to my mechanic, the entire passenger side of the engine is not firing intermittently. He seems to think the PCM is cooked and mentioned something about a portion of the wiring harness to the PCM being burnt. I haven't seen it since I dropped it off (friday) so i'll have to see what he was talking about this afternoon. After the price quote he gave me I think i'm going to shop around for a better quote. I'm not too familiar with working on cars with such computer based issues, is a PCM change something I can do on my own? or is it pretty much a dealer only service?

 

Changing the PCM is doable but I believe you need a dodge programmer to get things setup after you change it. I had mine replaced by the dealer with 8 new coils and at the same time let them flush the transmission cooler all for $1600. The PCM part in the 2500 was $400+ but I have heard they can run even more than that. I would guess that replacing the wiring between the PCM and coils would cost some money.