1997 Dodge Ram 1500 SLT Laramie, 4x4, 5.9L Magnum

Bought the truck for $1800 about two weeks ago. After putting a breather cap over an unnecessary opening in the passenger side valve cover (must be aftermarket opening for oil fill, but oil fill already present on driver side) and changing the oil and filter, I started getting misfire codes. I am assuming they were present when I bought it, and were just cleared since the idle was fairly rough when I drove it.

Anyway, here's the situation: The truck starts and drives perfectly fine, and there is no feeling of loss of power. The only symptoms are that it idles rough when rolling forward or in reverse (feels like the truck is bouncing) and the p0300 code accompanied by p0303, 4, and 5. Most recently it is now also shooting a code for cylinder 2. I also noticed that the oil pressure gauge starts to drop to the low end and sometimes illuminates the oil light when sitting at idle. This starts happening after driving for a bit, as the pressure is fine upon startup and for a little while after. As for performance, I don't feel like there is a noticeable loss of power, I do not believe I am burning oil at an alarming rate, but there MIGHT be some loss of efficiency, as a full tank has gotten me just over 200 miles (all city) and theres just under a quarter tank left. So all in all, my concerns lie with the misfire codes, oil pressure, and rough idle (not nearly as bad with brake applied or when in park).

Other threads have suggested I have a bad plenum gasket, but I just don't feel as though the symptoms add up to that, as I've not seen a misfire in C7 or C8, I don't appear to be burning too much oil, and I do not feel like I am losing power. The plugs and wires are all new (per seller), but I am about to pull them to make sure they aren't Bosch plugs (will update). I am not entirely familiar with Dodge or their trucks, so any input is welcomed and appreciated.

Update: Plugs are Champion Copper Plus (RC12YC)

 

Oil pressure is probably just the sensor. That is typical behavior for a failed one.

You can have a blown plenum, and NOT have the oil consumption. It sure wouldn't hurt to check, because, the rest of the symptoms are in line with that problem.

How many gallon gas tank?

See what your "new" parts look like, and especially how the plug wires are ran. There is a TSB in the FAQ section here for proper wire routing.

There probably should have been a tube from the valve cover, to the back of the air cleaner......

Welcome to DF!

 

Thanks! There is a line to the cleaner, the cap I put on was literally an extra opening. PCV, oil fill, and the line you're talking about are all there. The tank is a 26 gallon if I'm not mistaken. The recommended plugs are the ones installed. They look okay to me, but I'm no expert on how they should look. The wires were ziptied together, and all I did was undo those zipties since they were tight. The main reason I haven't done the plenum yet was lack of experience, time, and money. I could probably knock it out this weekend. I guess I just REALLY wanted it to be something stupid simple that I was missing. I just pulled the pcv and it rattles, but the grommet was super loose and there was a lot of grime around it. About to replace it. Just realized that the driver side of the air filter was super dirty and had oil in it. Gonna replace that too. Yet to check EGR valve as well. Thank you for the input, and I'll keep updating.

 

Hhhmmm... If you are getting oil into the air filter housing, that implies the PCV system isn't working as it should. That line is supposed to draw air INTO the engine, not out of it.

Definitely re-route your wires. Follow the TSB, see if that doesn't make a difference. (I bet it will )

If you just replace the gasket on the plenum plate, make sure to get shorter bolts. Or, just cut the unthread nubs off the ends.

 

Can you drop a link to the TSB for routing the wires? I can't find it...

 

Consider it dropped...


https://dodgeforum.com/forum/2nd-gen...lug-wires.html



.

 

Thank you. I will have to add this to my list of fixes this weekend.

 

So after replacing the plenum gasket and intake bolts (as well as all the other gaskets required for the job) I still have the same issue. I have rerun the plug wires with no improvement. The oil pressure gauge reads zero unless accelerating, but that is most likely just a failed sensor. I am replacing the upstream O2 sensor today, but I'm running out of ideas. Where else could I have a vacuum leak so drastic as to cause a rough idle? If it isn't a vacuum leak, what else could it be? I would think compression issues, maybe, but for it happen on a bunch of different cyclinders all at once?

 

Does it run decent at cold start, and then stumble off into crappy after a couple minutes? Or does it run like crap immediately?

 

It starts fine and runs fine while in park or stopped. You can kinda maybe sorta feel the intermittent miss at a stop, but that would be right from the get-go. The only real noticeable roughness is when you go to roll forward or backward in idle. It is fine while driving and when at a complete stop or in park.