I recently bought a 1994 Honda Civic VX, It has the stock D15z1. It has a misfire or stumble around 2k to 3k rpm. It is especially bad on the highway, it seems to be ok until the car is warmed up as well.
I have replaced the distributor, and checked timing with jumper jumped.
I have replaced cap, rotor, plugs, plug wires.
I double checked mechanical timing....this was part of the issue at first, it jumped a tooth but now it makes a lot more power but still has the hesitation.
I have replaced O2 sensor,
Put on a ebay header to make sure cat wasnt clogged before dropping money on a new cat
Replaced map sensor
Blocked off egr temporarily.
All of this has not fixed the problem.
Car has a new fuel pump and filter according to the previous owner. Compression test is good as well. Car does idle a little low when fully warmed up too but not a big deal if it would run on the highway ok. I am planning on doing a swap in the future but figuring that out here in California is gonna take some time and money and I would just like to drive the car as is until then.
Before i throw more money at this I would like to get a second opinion.

 

This is a PSA for people with a Civic VX / VEI that missfires. The solution to the problem is spelled: polyetheramine (P.E.A). I used Liqui Moly Direct Injection Cleaner and that fixed it. Hope this helps.