i just swapped out my d16z6 motor for a jdm zc motor, i swapped over my intake manifold, but thats it, my olf engine had low compression in one cylinder, and that was the only explination the shop could give me for the bogging, they recommended a jdm motor, i installed it and it ran good for about 750 miles, now it has started doing the same thing as my old one, when mine runs good u cant hear the vtec to well, but when it acts up the vtec gets loud as hell and it ont go anywhere, takes forever to get from 5000 rpm to redline, my old engine was backfiring from matting it to the floor just to keep up with traffic, this jdm motor hasnt backfired yet but from the way it sound i believe it will soon, when my old engine backfired it ran good after it did, but next time i drive it, it acts up again, anybody have this problem before, any suggestions would be greatly appreciated thanks

 

Check your plugs and spark plug wires.. You may be runnning on only 3 cylinders. Also, if you used your old o2 sensor, that could be the problem as well. There are a number of things that could be wrong. It could also be your timing.

What are your compression numbers? any CELs?

 

the o2 sensor would throw a code wouldnt it? i set the timing a week ago, plugs are new, wires are off my old engine, but if that was it why would it run good at first, the only light was the intake temp sensor and i replaced it and there is no codes now, i have open catylitic converter and the cat i took off was brand new looking on the inside, maybe the original cat broke apart and is clogging the the exhaust but when it backfires it opens back up and runs good for awhile