So I've got a 4.7l V8 in my Dakota. About a month ago I noticed the truck starting to run rough on cold starts, and slightly lagging acceleration. Over time it was getting worse, but my check engine light had still not come on until last week. Codes read P0300 Random multiple misfire, P0303, P0304, P0305, and P0307. Misfires in cylinders 3,4,5, and 7.

I had replaced the spark plugs and coil packs 15k miles ago. But I checked and replaced the spark plugs again anyway 2 days ago. The truck ran better, and a couple misfires went away. Misfires in cylinders 3 and 5 were still there. So I replaced the fuel injectors for those two cylinders, which got rid of the cylinder 3 misfire. But now I am at a loss.. Cylinder 5 is still misfiring, and I have no idea where to start looking from here. If anybody has some advice, I would greatly appreciate it!

 

Swap the COP with one from another cylinder and see if that changes anything. It could be failing.

After that, check compression.

 

Hey Life.
Just tossing some ideas at you if you haven't already thought of them.
1: Is the MAP sensor good?
2: Could a stretched timing chain or worn chain guides be throwing off the the ECU?
3: Is it possible one of the lash adjusters is sticking ?
anyway im sure you have already checked these things

 

Not sure what you mean by a COP.

Edit: I take that back, figured it out. When replacing the fuel injectors I had to remove all the coil packs, when I put them back in I had already swapped them around. So the cop is ruled out.

 

I actually have not checked any of these things. 1- what is a lash adjuster and how do I check it? 2- How would I troubleshoot the MAP sensor and timing chain?

 

COP (Coil On Plug). I have a 3.9L so I don't know how different they are however. Multiple misfires on my vehicle were caused by a bad crank sensor. On my truck I rotated the crankshaft having someone watch the rotor on the distributor to make sure there was no play between the two. I don't know if your truck has a distributor or not? Multiple misfires that give you no indication or it's confusing usually is caused by something else other then the cylinder and COP. It is usually a timing issue caused by cam sensor, crank sensor etc. From my experience anyway?

 

Since replacing the spark plugs it is no longer a random misfire. It is consistently cylinder #5 now. I do not have a distributor, and have already swapped around the coil packs, so those are not the issue. I also already have a new crankshaft sensor installed. Haven't replaced the camshaft sensor yet though.

 

Sorry if i missed it, but did you also change the plug wire on that cylinder? it could be arcing possibly. Try running the engine in the dark and look for wire arcing

 

The 4.7l engine doesn't have replaceable spark plugs and wires, as far as I know, they are actually part of the entire engine wiring harness. My ignition coils sit right on top of the spark plugs.

 

Ah! Ok It does sound like a bad COP though . or harness, All Copper core plugs?