I got a 97 dakota 3.9 manual transmission. 200k miles and it keeps giving me misfires on different cylinders. I've done plugs,wires, distributor cap, rotor, new injectors, new intake gasket, new plenum gasket. And it's still throwing misfire codes. Sometimes it's #3 sometimes the computer says random cylinder misfire. Sometimes it's 5 sometimes it's 6. I replaced all these things and it still has a miss. What next where do I look?

 

I would check fuel pressure next.

Also a weak coil could cause those symptoms.

 

I don't have a tester but when I hit the button on the side of the fuel rail it comes out good. And I pulled the plugs they seem to be sparking good. I'll go to the junkyard and get a coil pack

 

That is not a test. You require a minimum pressure for the injectors. Most auto parts store will lend or rent a fuel pressure tester. I recommend buying one.
Spark should be blue and able to jump 1/2 inch

 

3.9 has one coil they are around $15 and could be bad and show a spark.

 

I have the same problem out of my 02, after doing a complete tune up, the check engine light disappeared for one day, and then came back adding an O2 sensor on top of the random misfire.

So if you find anything, let me know please.

 

Let me know what you find out also ,i have the same problem with my 03

 

Jrox44 did you find what was causing misfires? Did the coil fix it?

 

This seems to be a problem with a high mileage engine 3.9L - I've had the same problem on #1 #3 #5 getting a misfire. I have replaced just about everything on this vehicle in the last year or so and no resolve. I've even tried a few different PCM's....not the answer. I'm down to 3 things now ... Engine compression test, timing chain, although looking at the distributor whilst turning the crank I really can't see any slop. and the final being the distributor itself although no indication of wear or play on the shaft. Even looked at that plastic piece below the hall effect transistor to make sure it didn't work loose from the rivets. mine is always #1 #3 #5. I used to get an occasional misfire on #3 a few years back. Problem is slowly getting worse so I guess I will eventually find out what it is. Anyway, great post and if anybody finds anything, please let us know.

 

Mine comes up on both sides of engine i have tried cap,rotor,swapped out coil cleared codes lasted a day misfires back again