I just bought a 2002 Dodge Dakota, single cab short bed 2wd. It has a 3.9 in it with almost 175k on it. It looks to be basically stock engine-wise other than a Spectre cold air intake. When I bought the truck it had battery issues but I believe I got rid of that.
It has been running a little on the rough side so I changed the oil and gave it a tune-up. This included 10w-30 oil, Bosch filter, new cap and rotor, NGK V-power 4291 plugs (it had Champion 7436 plugs in it when I pulled them out) and new Prestolite wires. I double-checked to make sure the wires were not put on wrong and made sure the NGKs were pre-gapped at .044. It runs a little smoother at idle but every other time I drive it, it hesitates and gives a popping noise when accelerating. It also shakes a bit too when running. It did this before I did the tune-up as well. There isn't a CEL on (although I'm thinking the codes could have been cleared from the previous owner).
I have a code scanner on order to see if any codes pop up, but in the mean time is there anything I can check or look for? I checked the fuses both in the cab and engine bay, nothing looks missing or burnt. I haven't checked the fuel system yet. Thanks.

 

Yeah it's a backfire, my truck does the same thing but only when its already warm and you go to start it up again. I always get P0303 (Cyl 3 Misfire) and sometimes P0301 (Cyl 1 Misfire).

I too have changed the plugs, wires, cap, rotor, coolant temp sensor and o2 sensors. I'm waiting for spring and then I'm going to do a compression test and my neighbour is also telling me to check the timing.

After that I dunno, if you fix yours let me know what it was.

Good luck.

 

You have the plugs gapped wrong. They are supposed to be .040 and not .044. Regap the plugs and see if that helps.

 

It might be a bad lifter. I'm not sure if the 3.9 is a OHV or OHC, but if your getting good spark and fuel then check your lifters next.

 

I took it to a mechanic who hooked it up to the Modis computer he had. He couldn't really find much because no codes popped up. The CEL came up after the alternator went out, I fixed the alternator and the CEL went off. I managed to pull a code P0175 which I guess means bank 2 is running rich, which is no surprise to me. The plugs on that side have a bunch of fuel on them. I think cylinders 3 and 5 are the backfire cylinders as the plugs are a bit black.
I had the mechanic check it out again, this time a little more in depth. He asked me to drive him around the block with the Modis connected, we got as far as backing up a few feet and he told me to just pull it back up since he could tell it was running horrible. He told me to check compression because he thinks a valve is bad.
I checked compression twice, all cylinders are between 148-150 PSI. Bad compression would mean either a valve or ring, correct? I'm kinda stumped until I talk with the mechanic again. Thanks.