I have a 1990 honda civic dx 1.5 lost all power all at once. Doesn't really want to go up hills. Changed fuel,air,spark plugs and oil filters. Idles sometimes seems a little off. When in third sometimes doesn't seem like the proper rpms when going over speed for that gear.

Have you had your exhaust checked out? Plugged catalytic converter can caus the problem your having or and exhaust restriction.

No not yet that is what I was going to do next. It does smoke a little at times so I was going to take off the catalytic converter and pound a strait pipe through it to see if it changed anything.