1998 Ford Ranger driving problem

When im driving down the road more in 3rd 4th and od. When I put more of a load on the vehicl it seems to jerk and almost like its missfiring. What do you think would be the cause of it? Timing, ignition, air intake. Also its throwing a code havn't had it checked yet.I thought it might be in the clutch but my buddy said it was like it was missfiring.I had a wird loose on the spark plug coil fixed that it does it still. Considering the truck has 2 plugs per cylinder. Possible a bad coil? It has 2 coils