Been having this issue for months now. Truck keeps getting worse and worse. Started it today and ran it came home left it running and sure enough its missing like mad. at idle, sounds like it has a damn cam in it with black smoke out the exhaust a little bit. I can merge onto the interstate or get on the gas and the check engine lights flashes nonstop them finally stays on. code says random cylinder misfire and then list several cylinders. Plugs are ngk about 4 months old, new cap and rotor button, msd wires, msd coil, fuel pump was replaced in 09 with chrysler unit. Last winter i replaced the upper/lower intake gaskets. coolant level stays full so its not a head gasket leak. o2 sensors were replaced 3 years ago with bosch ones. I have cleaned,checked,and determined that all grounds are hooked up correctly. Im stumped.......This is on a 97 dakota but i know that alot of you ram guys also have the 318. I just need some input

 

You mentioned intake gaskets. Does this also include the plenum gasket on the bottom of the intake manifold? If so, did you use the original steel plate? If so, the gasket may have blown again. Needs to be replaced with a 1/4" aluminum plate to hold up.

You mentioned O2 sensors, but your symptoms also may be related to clogged cat. Pull upstream O2 sensr out and tie it back out of the way and start truck. See if it runs better. If so, cat is clogged and needs to be replaced.

Check these and let us know! (can't believe I beat zman to the plenum and cat thinggy! Whoop!)

 

Cats a high flow unit and is new. Yes, i did the plenum gasket but reused the stock bottom plate. I reused it because i used permatex for a gasket maker.

 

From what I've seen on here, you need to ditch the Bosch o2 sensers. They don't get along well with the ECU and such. Go with NTK.

And x2 on what gd said. Also check fuel pressure. Should be same as the Rams I would assume, 49psi, iirc.

 

The lower intake gasket is most likely blown again and your new cat is clogged. Using Permatex means nothing and will NOT work. Also the factory pan bolts are too long. You used gasket maker without a gasket?

 

I used permatex WITH a gasket. Looking down the throttle body the pan is still clean. no oil build up or residue. New cat clogged??? A NEW cat? Truck runs too good to be a clogged cat. only time a misfire can be heard or felt is at idle. Above 500 rpm the truck performs like it did brand new.

 

What plugs are you running; and pull each one by one and check the core for burn marks and heat spots on the outer rim.. and compare with one another and see if any of them are worse off than the others.. i fixed one kinda miss thing by a rocker arm but i still have an idle 'lope' and sounds like a cam in my truck.. 5.2L 97'... My number 3 has a burn mark that is darker and blacker than the rest of my plugs; those have the same but are more of a light grey. I suspect there is a hot spot of carbon build up in that cyl. At least thats what some have suggested to me around here; Ill be replacing with autolights soon enough.

Example Photo:

 

check your distrubuter cap bc mine was doing the same thing last yr at idle it ran ruff and sounded like it was going to stall but after u got going it was fine...check the distrubuter cap or just get a new one dont cost much

 

Im running nkg plugs that are about 4 months old. gap is good and all 8 plugs look exactly the same....

 

Distributor cap is solid and tight. Its only a few months old and i even cleaned the terminals with a wire wheel on a dremel.